ALTERATIONS IN THE DIRECTION OF ORGANS.
The deviations from the ordinary direction of organs partake for the
most part more of the nature of variations than of absolute malposition
or displacement. It must also be borne in mind how frequently the
direction of the leaves, or of the flower, varies according to the
stage of development which it has arrived at, to unequal or
disproportionate growth of some parts, or to the presence of some
impediment either accidental or resulting from the natural growth of the
plant. These and other causes tend to alter the direction of parts very
materially.
=Change in the direction of axile organs, roots, stems, &c.=--The roots
frequently exhibit good illustrations of the effect of the causes above
mentioned in altering the natural direction. The roots are put out of
their course by meeting with any obstacle in their way. Almost the only
exception to the rule in accordance with which roots descend under
natural circumstances, is that furnished by _Trapa natans_, the roots of
which in germination are directed upwards towards the surface of the
water. So in _Sechium edule_, the seed of which germinates while still
in the fruit, the roots are necessarily, owing to the inverted position
of the embryo, directed upwards in the first instance.
A downward direction of the stem or branches occurs in many weak-stemmed
plants growing upon rocks or walls, or in trees with very long slender
branches as in _Salix Babylonica_, and the condition may often be
produced artificially as in the weeping ash.
The opposite change occurs in what are termed fastigiate varieties,
where the branches, in place of assuming more or less of a horizontal
direction, become erect and nearly parallel with the main stem as in the
Lombardy poplar, which is supposed to be merely a form of the black
Italian poplar.
M. de Selys-Longchamps has described a similar occurrence in another
species of Poplar (_P. virginiana_ Desf.), and amongst a number of
seedling plants fastigiate varieties may frequently be found, which may
be perpetuated by cuttings or grafts, or sometimes even by seed; hence
the origin of fastigiate varieties of elms, oaks, thorns, chestnuts, and
other plants which may be met with in the nurseries.
Sometimes when the top of the main stem is destroyed by disease or
accident, one of the heretofore lateral shoots takes its place, and
continues the development of the tree in the original direction. It is
often an object with the gardener to restore the symmetry of an injured
tree so that its beauty may ultimately not be impaired.[210]
Climate appears sometimes to have some influence on the direction of
branches, thus Dr. Falconer, as quoted by Darwin,[211] relates that in
the hotter parts of India "the English Ribston-pippin apple, a Himalayan
oak, a Prunus and a Pyrus all assume a fastigiate or pyramidal habit,
and this fact is the more interesting as a Chinese tropical species of
_Pyrus_ naturally has this habit of growth. Nevertheless many of the
fastigiate varieties seen in gardens have originated in this country by
variation of seeds or buds."
M. Carriere has also recorded a curious circumstance with reference to
the fastigiate variety of the false acacia _Robinia pseudacacia_; he
states that if a cutting or a graft be taken from the upper portion of
the tree, the fastigiate habit will be reproduced, and the branches will
be furrowed and covered with short prickles; but if the plant be
multiplied by detaching portions of the root-stock, then instead of
getting a pyramidal tree with erect branches, a spreading bushy shrub is
produced, with more or less horizontal, cylindrical branches, destitute
of prickles.[212]
=Eversion of the axis.=--In the case of the fig, the peculiar
inflorescence is usually explained on the supposition that the
termination of the axis becomes concave, during growth, bearing the true
flowers in the hollow thus formed. The cavity in this case would
probably be due not to any real process of excavation, but to a
disproportionate growth of the outer as contrasted with the central
parts of the fig. Some species of _Sempervivum_ have a similar mode of
growth, so that ultimately a kind of tube is formed, lined by the
leaves, the central and innermost being the youngest. The hip of the
Rose may be explained in a similar manner by the greater proportionate
growth of the outer as contrasted with the central portions of the apex
of the flower-stalk. In cases of median prolification, already referred
to, the process is reversed, the central portions then elongate into a
shoot and no cavity is formed. A fig observed by Zuccarini (figs. 105,
106) appears to have been formed in a similar manner, the flower-bearing
summit of the stalk not being contracted as usual, the flowers projected
beyond the orifice of the fig. If this view be correct the case would be
one rather of lengthening of the axis than of absolute eversion since it
was never inverted.
[Illustration: FIG. 105.--Fig showing prolonged inflorescence and
projecting flowers.]
[Illustration: FIG. 106.--Section of the same.]
=Altered direction of leaves.=--The leaves partake more or less of the
altered direction of the axis, as in fastigiate elms, but this is not
universally the case, for though the stem is bent downwards the leaves
may be placed in the opposite direction; thus in some specimens of
_Galium Aparine_ growing on the side of a cliff from which there had
been a fall of chalk, the stems, owing apparently to the landslip, were
pendent, but the leaves were abruptly bent upwards.
One of the most singular instances of an inverted direction of the
leaves is that presented by a turnip (fig. 107) presented to the Museum
of King's College, London, by the late Professor Edward Forbes. The
turnip is hollow in the interior and the majority of the leaves
springing from its apex instead of ascending into the light and air
become bent downwards so as to occupy the cavity, and in such a manner
as to bring to mind the position of an inverted embryo in a seed.
[Illustration: FIG. 107.--Hollow turnip, showing some of the leaves
inverted and occupying the cavity.]
=Altered direction of the flower and its parts.=--The changes which take
place in the relative position either of the flower as a whole or of its
several parts during growth are well known, as also are the relations
which some of these movements bear to the process of fertilisation, so
that but little space need here be given to the subject beyond what is
necessary to point out the frequent changes of direction which
necessarily accompany various deviations from the ordinary form and
arrangement of parts.
In cases where an habitually irregular flower becomes regular, the
change in form is frequently associated with an alteration in direction
both of the flower as a whole and, to a greater or less extent, of its
individual members, for instance of _Gloxinia_, the normal flowers of
which are irregular and pendent, there is now in common cultivation a
peloriate race in which the flowers are regular in form and erect in
position.
[Illustration: FIG. 108.--Flower of normal _Gloxinia_.]
[Illustration: FIG. 109.--Flower of _Gloxinia_, erect and regular
(regular _Peloria_).]
Fig. 108 shows the usual irregular form of _Gloxinia_, with which may be
contrasted figs. 109, 110 and 111.
Fig. 109 shows the regular erect form; fig. 110 the calyx of the same
flower; while in fig. 111 are shown the stamens and style of the two
plants respectively. In the upper figure the style of the peloriate
variety is shown as nearly straight, and the stamens undergo a
corresponding change. No doubt the relative fertility and capacity for
impregnation of the two varieties is affected in proportion to the
change of form. The Gloxinia affords an instance of regular congenital
peloria in which the regularity of form and the erect direction are due
to an arrest, not of growth, but of development, in consequence of which
the changes that ordinarily ensue during the progress of the flower from
its juvenile to its fully formed condition do not take place.
[Illustration: FIG. 110.--Calyx of erect _Gloxinia_.]
[Illustration: FIG. 111.--Stamens of erect regular, and of pendent
irregular-flowered _Gloxinia_.]
A similar alteration accompanies this form of peloria in other flowers
(see Peloria). A change in direction may result also from other
circumstances than those just alluded to. Abortion or suppression of
organs will induce such an alteration; thus in a flower of _Pelargonium_
now before me three of the five carpels, from some cause or other, are
abortive and much smaller than usual, and the style and the beak-like
torus are bent downwards towards the stunted carpels instead of being,
as they usually are, straight.
Amongst orchids, where the pedicel of the flower or the ovary is
normally twisted, so that the labellum occupies the anterior or inferior
part of the flower, it frequently happens, in cases of peloria and other
changes, that the primitive position is retained, the twist does not
take place, and so with other resupinate flowers. In Azaleas a curious
deflexion of the parts of the flower may occasionally be met with. Fig.
112 shows an instance of this in which the corolla, the stamens and the
style were abruptly bent downwards: as young flowers of this singular
variety have not been examined it is difficult to form an opinion as to
the cause of this variation. In one plant the change occurred in
connection with the suppression of all the flowers but one in the
cluster, or rather the place of the flowers was occupied by an equal
number of leafy shoots.
[Illustration: FIG. 112.--Flower of _Azalea_, showing the corolla
reflected.]
Moquin[213] mentions a flower of _Rosa alpina_ in which two of the
petals were erect, while the remaining ones were much larger and
expanded horizontally. The same author quotes from M. Desmoulins the
case of a species of _Orobanche_, in which a disjunction of the petals
constituting the upper lip took place, thus liberating the style and
allowing it to assume a vertical direction.
[Illustration: FIG. 113.--Flower of _Cuphea miniata_ enlarged, showing
protrusion and hypertrophy of an erect placenta, after Morren.]
[Illustration: FIG. 114.--Placenta from the flower shown at fig. 113;
the ovary is membranous and torn, the placenta, erect and ovuliferous,
after Morren.]
M. Carriere[214] has described an instance wherein two apples were
joined together, a larger and a smaller one; the former was directed
away from the centre of the tree as usual, while the smaller one was
pointed in exactly the opposite direction. The larger fruit had the
customary parchment-like carpels, the smaller was destitute of them.
Sometimes the direction assumed by one flower as an abnormal occurrence
is the same as that which is proper to an allied species or genus under
natural circumstances; thus flowers of the vine (_Vitis_) have been met
with in which the petals were spreading like a star (_fleurs
avalidouires_), as in the genus _Cissus_.[215]
Morren describes a curious condition in some flowers of _Cuphea
miniata_, in which the placenta protruded through an orifice in the
ovary, and losing the horizontal direction became erect (figs. 113,
114). A similar occurrence happened in _Lobelia erinus_. To this
condition the Belgian savant gave the name of gymnaxony.[216]
FOOTNOTES:
[210] The following details as to the method pursued by Mr. McNab, of
the Edinburgh Botanic Garden, may not be uninteresting in this place.
They are from the pen of Mr. Anderson, and originally appeared in the
'Gardeners' Chronicle.'
"The mode of inducing leaders to proceed from laterals is a matter of
comparatively little concern among the generality of deciduous trees,
for they are often provided with subsidiary branches around the leader,
at an angle of elevation scarcely less perpendicular, but the laterals
of all Conifers stand, as nearly as possible, at right angles. Imagine
the consternation of most people when the leader of, say, _Picea
nobilis_, _P. Nordmanniana_, or _P. Lowii_ is destroyed."
In a specimen of the latter plant the leader had been mischievously
destroyed, to remedy which Mr. McNab adopted means which Mr. Anderson
goes on to describe. "Looking from the leader downward to the first tier
of laterals, there appeared to have been a number of adventitious
leaf-buds created, owing to the coronal bud being destroyed. These were
allowed to plump up unmolested until the return of spring, when every
one was scarified or rubbed off but the one nearest the extremity. To
assist its development and restrain the action of the numerous laterals,
every one was cut back in autumn, and this restraint upon the sap acted
so favorably upon the incipient leader as to give it the strength and
stamina of the original leader, so that nothing detrimental was evident
twelve months after the accident had happened, and only a practical eye
could detect that there had been any mishap at all. This beautifully
simple process saved the baby tree.
"Another example of retrieving lost leaders may be quoted as
illustrative of many in similar circumstances. _Picea Webbiana_ had its
leader completely destroyed down to the first tier of laterals. There
was no such provision left for inducing leaf-buds as was the case with
_P. Lowii_ above referred to. Resort must, therefore, be had to one of
the best favoured laterals, but how is it to be coaxed from the
horizontal position of a lateral to the perpendicular position of a
leader? The uninitiated in these matters, and, in fact, practical
gardeners generally, would at once reply, by supporting to a stake with
the all-powerful Cuba or bast-matting. But no. A far simpler method than
that, namely, by fore-shortening all the laterals of the upper tier but
the one selected for a leader. Nature becomes the handmaid of art here;
for without the slightest prop the lateral gradually raises itself
erect, and takes the place of the lost leader. All that the operator
requires to attend to is the amputation of the laterals until this
adventitious fellow has gained a supremacy. Singular provision in nature
this, which, thanks to the undivided attention of a careful observer,
has been fully appreciated and utilized."
[211] 'Variation of Animals and Plants,' ii, p. 277.
[212] Quoted in 'Gard. Chron.,' 1867, p. 654.
[213] Loc. cit., p. 315.
[214] 'Rev. Hortic.,' 1868, p. 110.
[215] Planchon and Mares, 'Ann. Sc. Nat.,' 5 ser., tom. vi, 1866, p.
228, tab. xii.
[216] 'Bull. Acad. Belg.,' xviii, part ii, p. 293.
BOOK II.
DEVIATIONS FROM THE ORDINARY FORM OF ORGANS.
In a morphological point of view the form of the various parts or organs
of plants and the changes to which they are subjected during their
development are only second in importance to the diversities of
arrangement and, indeed, in some cases, do not in any degree hold a
second place.
Taken together, the arrangement, form, and number of the several parts
of the flower, make up what has been termed the symmetry of the
flower.[217] Referring to the assumed standard of comparison, see p. 4,
it will be seen that in the typically regular flower all the various
organs are supposed to be regular in their dimensions and form. At one
time it was even supposed that all flowers, no matter how irregular
they subsequently became, began by being strictly symmetrical or
regular, and that subsequent alterations were produced by inequality of
growth or development. The researches of organogenists have, however,
dispelled this idea of unvarying primordial regularity, by showing that
in many cases flowers are irregular from the very first, that some begin
by being irregular, and subsequently become regular, and even in some
cases resume their original condition during the course of their
development.[218] Under these circumstances an artificial standard of
comparison becomes almost an absolute necessity for the time being.
Changes of form very generally, but not always, are accompanied with a
change in regularity: thus a flower habitually bi-lateral may assume the
characters of radiating symmetry and _vice versa_. Increase or decrease
of size very frequently also are co-existent with an alteration in the
usual form.
In the case of the arrangement of organs it is often difficult or
impossible, in the present state of our knowledge, to determine whether
a given arrangement is congenital or acquired subsequently to the first
development, whether for instance an isolation of parts be due to
primordial separation or to a subsequent disunion of originally combined
organs, see p. 58. With reference to the changes in the form of organs,
however, it is in general more easy to ascertain the proximate cause of
the appearance, and thus teratological changes of form may be grouped
according as they are due to, 1, arrest of development; 2, undue or
excessive development; 3, perverted development; and 4, irregular
development; hence the use of the following terms--Stasimorphy,
Pleiomorphy, Metamorphy, and Heteromorphy--to include teratological
changes really or apparently due to one or other of the causes above
mentioned. The classification here adopted is of course to a
considerable extent an arbitrary one and subject to correction or
modification, as the knowledge of the development of the flowers in the
various genera of plants advances.
FOOTNOTES:
[217] The word symmetry has been used in very different senses by
different botanists, sometimes as synonymous with "regularity," at other
times to express the assumed typical form of a flower. Payer understands
it to be that arrangement of parts which permits of the whole flower
being divided vertically into two symmetrical halves (bi-lateral
symmetry). Others, again, have applied the term symmetry to the number
of the parts of the flower, reserving the terms "regularity" or
"irregularity" for the form. It is here used in a general sense to
express the plan of the flower, and thus includes the arrangement, form,
and number of its component elements.
[218] See Baillon, 'Adansonia,' v, 176.
PART I.
STASIMORPHY.[219]
Deviations from the ordinary form of organs arising from stasis or
arrest of development are included under this heading.
There are many cases in which the forms proper to a juvenile condition
of the plant are retained for a much longer period than ordinary, or
even throughout the life of the individual growth goes on, but
"development" is checked. Such conditions may even be propagated by seed
or bud. It is a very general thing for botanists to consider these cases
as reversions to a simpler, primitive type, and this may be so; but on
the other hand, they may be degenerations from a complex type, or they
may have no direct relation to any antecedent condition. Stasimorphic
changes affecting principally the relative size of organs--such, for
instance, as the non-development of internodes, or the atrophy or
suppression of parts will be found mentioned in the sections relating to
those subjects. In the present part those alterations which affect the
form of organs principally are treated of.
FOOTNOTES:
[219] [Greek: Stasis-morphosis].
CHAPTER I.
PERSISTENCE OF JUVENILE FORMS.
The retention in adult life of a form characteristic of an early stage
of development, and therefore usually transient, may be manifested in
any of the organs of the plant. As these cases are for the most part
treated under separate headings, it is here only necessary to allude to
a few, which it is difficult to allocate satisfactorily, while the
reader may be referred for other instances of like nature to the
sections on Peloria, Atrophy, Suppression, Dimorphy, Substitutions, &c.
[Illustration: FIG. 115.--_Juniperus sinensis_. Two forms of leaves on
branches of the same shrub.]
=Stasimorphy in the leaves of conifers.=--In many conifers the leaves
produced in the young state of the plant are different, both in
arrangement and form, from those subsequently developed (see pp. 89,
90). But it occasionally happens that the plant continues to form
throughout its existence leaves such as are usually produced only in a
young state; thus M. Gubler ('Bull. Soc. Bot., Fr.,' vol. viii, 1861, p.
527) describes a plant of _Pinus pinea_ in which the primordial, usually
transitory, foliage was permanent, leaves of the ordinary shape not
being developed at all. It more often happens that some only of the
leaves retain their young form while others assume other shapes, see
fig. 115. This happens frequently in the larch and constantly in the
Chinese juniper when it has arrived at a considerable age. In _Cupressus
funebris_ two forms of leaves may often be found on the same plant, the
one representing the juvenile state, the other the more developed
condition. What is very singular, is that a cutting taken from the
branch with leaves of the young form grows up into a shrub bearing
leaves of no other shape, so that an ordinary observer unacquainted with
the history of the plant would imagine that he had to deal with two
distinct species. This fact is the more interesting when compared with
the alternation of generations which takes place among the lower
animals.
The regular development of all the parts of the flower in a plant
habitually producing irregular flowers is referred to under the head of
Peloria, but it still remains to consider those examples in which some
only of the parts of the flower are affected in this manner.[220] Most
of these cases are elsewhere referred to in this volume under the
particular form of malformation assumed; but the following case may here
be noticed as not coming under any of the previous heads. It is an
instance recorded by Professor Babington ('Phytologist,' August, 1853),
and in which the pod of _Medicago maculata_, which is usually rolled up
like a snail shell and provided with spines, was sickle-shaped and
unarmed.
FOOTNOTES:
[220] See a paper of Professor C. Morren's on "Floral Stesomy" in 'Bull.
Acad. Belg.,' t. xix, part ii, p. 519.
CHAPTER II.
REGULAR PELORIA.
[Illustration: FIG. 116.--Regular Peloria, _Delphinium_.]
[Illustration: FIG. 117.--Sepal, petal, &c., of regular-flowered
_Delphinium_.]
[Illustration: FIG. 118--Regular peloria, _Viola_.]
[Illustration: FIG. 119--Double Violet, flower regular, petals
multiplied, stamens and pistils petaloid.]
When an habitually irregular flower becomes regular, it does so in one
of two ways; either by the non-development of the irregular portions, or
by the formation of irregular parts in increased number, so that the
symmetry of the flower is rendered perfect, as in the original peloria
of Linnaeus, and which may be called irregular peloria, while the former
case may be called regular peloria. This latter appearance is therefore
congenital, and due to an arrest of development.[221] As the true nature
of these cases has not been in all cases recognised (even Moquin places
them under the head of deformities--they being less entitled to rank in
that class than are the usual flowers), it may be well to cite a few
instances taken from various families. In _Delphinium peregrinum_ I have
met with perfectly regular flowers having five sepals and five oblong
stalked petals, and a similar occurrence has been noted in other
species of this genus. Baillon,[222] in referring to these flowers,
points out the resemblance that they bear to the double varieties of
_Nigella_. In the stellate columbines (_Aquilegia_) of gardens the
tubular petals are replaced by flat ones often in increased numbers. In
violets both forms of peloria occur, that in which there is an unusual
number of spurs, and that in which there are no spurs (var. anectaria).
In the more perfect forms of regular peloria occurring in the last-named
genus the following changes may be noticed: 1, an alteration in the
direction of the flower so that it remains in an erect position, and is
not bent downwards as usual; 2, equality of proportion in the sepals and
petals; 3, absence of spurs, as also of hairs on the lateral petals; 4,
equal stamens whose anthers are sometimes entirely destitute of the
prolonged crest which forms so prominent a feature under ordinary
circumstances; 5, erect, not curved styles, and the stigmas not
prolonged into a beak, but having a more or less capitate form; ovary
with three or five cells, ovules normal.
These are cases where the change in question is most strongly marked,
the bi-lateral is completely replaced by the radiating symmetry. The
absence of the usual nectary, and of hairs on the side petals, the
alterations in the form of the style, etc., all show how much the
process of fertilisation must be altered from that which occurs under
ordinary circumstances. In some of the double violets now cultivated in
gardens, a similar regularity of proportion in the parts of the flower
may be seen combined with the substitution of petals for stamens and
pistils, and with the development of an increased number of petal-like
organs.[223] Between these cases and the ordinary spurred forms as well
as those with an increased number of spurs, many intermediate forms may
be met with. That such regularity should occur in this family is not to
be wondered at seeing that there is a whole subdivision of the order
(_Alsodeiae_) in which regular flowers are the rule.
In cultivated Pelargoniums the central flower of the umbel or "truss"
frequently retains its regularity of proportion, so as closely to
approximate to the normal condition in the allied genus _Geranium_; this
resemblance is rendered greater by the fact that, under such
circumstances, the patches of darker colour characteristic of the
ordinary flower are completely wanting; the flower is as uniform in
colour as in shape. Even the nectary which is adherent to the upper
surface of the pedicel in the normal flower disappears--sometimes
completely, at other tunes partially. The direction of the stamens and
style, and even that of the whole flower, becomes altered from the
inclined to the vertical position. In addition to these changes, which
are those most commonly met with, the number of the parts of the flower
is sometimes augmented, and a tendency to pass from the verticillate to
the spiral arrangement manifested. Schlechtendal mentions some flowers
of _Tropaeolum majus_ in which the flowers were perfectly regular and
devoid of spurs[224], while in the double varieties, now commonly grown
in greenhouses, the condition of parts is precisely the same as in the
double violet before alluded to. Among the _Papilionaceae_ the Laburnum
and others have been noticed to produce occasionally a perfectly regular
flower in the centre, or at the extremity of the inflorescence, though
the peloria in this flower is usually irregular. In the Gentianaceous
genus _Halenia_, _H. heterantha_ is remarkable for the absence of spurs.
Amongst _Gesneraceae_, _Bignoniaceae_, _Scrophulariaceae_, and other
families of like structure, regular peloria is not uncommon. Fig. 120
represents a case of this kind in _Eccremocarpus scaber_, conjoined, as
is frequently the case, with dialysis or separation of the petals.[225]
Many of the cultivated Gloxinias also show erect, regular, five
stamened flowers, but these are probably cases of irregular peloria.
[Illustration: FIG. 120.--Regular peloria, _Eccremocarpus scaber_.]
A solitary flower of _Pedicularis sylvatica_ was found by the Marquis of
Stafford near Dunrobin Castle in Sutherlandshire, in which the usual
ringent form of the corolla was replaced by the form called
salver-shaped. There were six stamens, four long and two short. Sir W.
Hooker and Mr. Borrer are stated to have found a similar flower in the
same locality in 1809.[226]
The passage of ligulate to tubular corollas among _Compositae_ is not of
such common occurrence as is the converse change. I owe to Mr. Berkeley
the communication of a capitulum of a species of _Bidens_, in which
there was a transition from the form of ligulate corollas to those that
were deeply divided into three, four, or five oblong lobes. These then
were instances of regular peloria.
[Illustration: FIG. 121.--Flower of _Cattleya marginata_. Lip replaced
by a flat petal.]
In _Orchidaceae_ a similar change is not by any means infrequent; in a
few, indeed, a regular flower is the normal character, as in
_Dendrobium normale_, _Oncidium heteranthum_, _Thelymitra_, etc. Fig.
121, reduced from a cut in the 'Gardeners' Chronicle,' 1854, p. 804,
represents an instance of this kind in _Cattleya marginata_.
From the same journal the following account of a case of peloria in
_Phalaenopsis Schilleriana_ is also cited as a good illustration of this
peculiar change. The terminal flower differed entirely from all the
others; instead of the peculiar labellum there were three petals all
exactly alike, and three sepals also exactly alike; the petals resembled
those of the other flowers of the spike, and the upper sepal also; but
the two lower sepals had no spots, and were not reflexed as in the
ordinary way: thus, these six parts of the flower were all in one plane,
and being close together at their edges, made almost a full round
flower; the column and pollen-glands were unaffected. Professor
Reichenbach also exhibited at the Amsterdam Botanical Congress, of 1865,
a flower of _Selenipedium caudatum_ with a flat lip.
M. Gris[227] has placed on record some interesting cases of peloria of
this kind in _Zingiber zerumbet_; in the more complete forms the
androecium or staminal series was composed of six distinct pieces, the
three inner of which were fertile, while in the ordinary flower the
androecium is composed of two pieces, "a lip" and a fertile stamen.
"Is it not a matter of regret," says M. Gris, "to be obliged to call the
latter the normal flower?"
Under this head may likewise be mentioned those cases in which the
normal, or at least the typical symmetry of the flower is restored by
the formation of parts usually suppressed; thus Moquin cites an abnormal
flower of _Atriplex[228] hortensis_ described by M. Fenzl as having a
true calyx within the two bracts that usually alone encircle the
stamens. Adanson, also cited by Moquin, found a specimen of _Bocconia_
with a corolla. _Arum maculatum_ has likewise been met with provided
with a genuine perianth as in _Acorus_ and other Orontiads. The unusual
development of the sexual organs in diclinous flowers has been alluded
to under the head of heterogamy, and other cases where the symmetry of
the flower is rendered regular, by the development of parts ordinarily
suppressed, will be found in the chapters relating to deviations from
the usual number of organs.
This change, or rather this persistence of a form that is usually
transient, is generally accompanied by some other alterations. Change of
direction, as has been already mentioned, is one of the most common of
these; separation of the petals (_Antirrhinum_, _Verbascum_, &c.), and
even their appearance in leaf-like guise, are not infrequent
(_Delphinium_, _Antirrhinum_, _Verbascum_, &c.) At other times
multiplication or increased number of the whorls of petals takes place,
often, but not always, at the expense of the sexual organs of the
flower. Perhaps even more frequent is the increased number of parts in
the same whorl in cases of regular peloria; thus, in the Pelargoniums
before alluded to, the parts of the flower are frequently regulated by
the number six instead of five.
This form of peloria is most generally met with in flowers that are
placed at the end or in the centre of the inflorescence, or in such
flowers as occur singly at the end of the flower-stalk, as in
_Tropaeolum_, _Viola_, &c. It would hence seem as if the freedom from
pressure or restriction on one side allowed the flower to develop
equally in all directions, and thus to produce regularity of form.
It is obvious, from what has been before said, that the process of
fertilisation is in many cases interfered with and altered by the change
in the conformation or the flower.
From overlooking the occasional existence of this form of peloria, new
genera have sometimes been formed on insufficient grounds. The genus
_Aceranthus_, for instance, consists of species of _Epimedium_ in which
the customary spurs are not formed.[229]
The occurrence both of regular and irregular peloria on the same plant
has frequently been observed in _Linaria_. It has also been remarked
that the seedlings raised from these forms are not always constant;
thus, the late Mr. Crocker, formerly foreman in the Royal Gardens, Kew,
informed me that he fertilised some flowers of a drooping Gloxinia with
their own pollen, and that when the seedlings blossomed a large number
of them produced the erect regular flowers.
From what has been already said it will be seen that regular peloria is
closely allied to what Morren called epanody, or a return to the normal
condition. The reversion of a monstrous form to the normal one, as, for
instance, when the fern-leaved beech reverts to the normal type, was
called by the same author epistrophy.[230]
The following are the genera in which regular peloria has been most
often observed. It must, however, be remarked that in some of the
flowers recorded as peloric there is no indication as to which form of
peloria the case should be referred to. For other illustrations refer to
chapters on Heterogamy, Number, Irregular Peloria, &c.
*Delphinium peregrinum!
*Nigella damascena!
*Aquilegia vulgaris!
*Viola odorata!
hirta.
Epimedium, sp.
*Pelargonium zonale!
* inquinans!
Tropaeolum majus!
*Wistaria sinensis.
Lupinus.
*Cytisus Laburnum!
Trifolium repens!
*Compositae, gen. pl.!
Lonicera Periclymenum!
Streptocarpus Rexii.
*Digitalis purpurea.
*Scrophularia aquatica.
*Pentstemon.
*Linaria vulgaris!
*Antirrhinum majus!
Verbascum nigrum!
Columnea Schiedeana.
Halenia heterantha.
Galeobdolon luteum.
Prunella vulgaris!
Salvia, sp.!
Teucrium campanulatum.
Betonica alopecuros.
Eccremocarpus scaber.
Pedicularis sylvatica.
Zingiber Zerumbet.
Phalaenopsis amabilis!
Phalaenopsis Schilleriana.
Habenaria.
*Orchis morio.
mascula.
*Dendrobium, sp.
Atriplex, sp.
Cattleya Mossiae!
marginata.
Calanthe vestita!
Oncidium, sp.!
Selenipedium caudatum.
Arum maculatum.
In addition to the references already given, further information on this
subject may be gained from consulting the following publications. See
also Irregular Peloria.
Giraud, 'Bot. Soc. Edinb.,' Dec. 12, 1839, _Antirrhinum_.
Dareste, 'Ann. Sc. Nat.,' ser. 2, 1842, xviii, p. 220,
_Delphinium_. C. Morren, 'Fuchsia,' p. 90, _Calceolaria_,
'Bull. Acad. Belg.,' xx, part ii, p. 57; and E. Morren, 'Bull.
Acad. Belg.,' 2nd ser., xix. p. 224, _Gloxinia_. Richard, 'Mem.
Soc. d'hist. nat.,' ii, p. 212, tab. 3. Lindley, 'Journ. Linn.
Soc.,' iii, p. 9, _Dendrobium_. Michalet, 'Bull. Soc, Bot.
France,' vii, p. 625, _Betonica_. Gubler, 'Bull. Soc. Bot.
Fr.,' ix, 81, 'Des anomalies aberrantes et regularisantes.'
Reichenbach fil. 'De pollinis orchid. genesi ac structura,'
1852, _Oncidium_. Clos, 'Mem. Acad. Toulouse,' vi, 1862,
_Salvia_. Caspary, 'Verhandl. Phys. OEkon. Gesell.
Koenigsberg,' 1860, i, 59, _Columnea_. Bureau, 'Bull. Soc. Bot.
Fr.,' 1861, vol. viii, p. 710, _Streptocarpus_. Darwin,
'Variation of Animals and Plants,' ii, pp. 59 and 396. Godron,
'Ex. Bull. Bot. Soc. Fr.,' xiv, p. 165, 'Rev. Bibl.,'
_Wistaria_. Marchand, 'Adansonia,' iv, p. 172, _Lonicera_.
Baillon, 'Adansonia,' v, p. 177, 'Sur la regularite transitoire
de quelques fleurs irreg.,' shows that during the development
of some flowers which begin and end by being irregular, there
is an intermediate state when all the parts are regular. Helye,
'Revue Horticole,' Sept., 1868, p. 327. In this last paper,
published as this sheet is going through the press, the author
states that he has raised from seed three generations of plants
of _Antirrhinum_ with regular spur-less flowers. The original
wild plant was only partially peloric, but all the flowers
produced on its descendants were regular.
FOOTNOTES:
[221] "On the existence of two forms of Peloria," by M. T. Masters.
'Nat. Hist. Review,' April, 1863.
[222] Baillon, 'Adansonia,' iv. p. 149.
[223] Similar cases are figured in 'Hort. Eystettens. Ic. Pl. Vern.'
fol. 4, f. 1, 2. _Viola martia_ multiplici flore.
[224] 'Linnaea,' 1837, p. 128.
[225] M. Bureau, 'Bull. Soc. Bot. Fr.,' ix, p. 91, describes two genera
of _Bignoniaceae_ in which the flowers are _normally_ regular and six
parted.
[226] See 'Trans. Linn. Soc.,' vol. x. p. 227.
[227] 'Ann. Sc. Nat.,' ser. 4, 1859. tom. xi, p. 264, tab. 3.
[228] 'El. Ter. Veg.,' p. 342.
[229] Marchand, 'Adansonia,' vol. iv, p. 127.
[230] 'Bull. Acad. Belg.,' xvii. p. 17. "Fuchsia," p. 169.
PART II.
PLEIOMORPHY.[231]
Most irregular flowers owe their irregularity to an unequal development
of some of their organs as compared with that of others. When such
flowers become exceptionally regular they do so either because
development does not keep pace with growth, and a regular flower is thus
the result of an arrest of the former process (regular peloria), or
because the comparatively excessive development, which usually occurs in
a few parts is, in exceptional cases manifested by all, hence the flower
becomes regular from the increase in number of its irregular elements.
These latter cases, then, are due to an excess of development, hence the
application of the term pleiomorphy. It must be understood that mere
increase in the number of the organs of a flower is not included under
this head, but under that of deviations from the ordinary number of
parts.
FOOTNOTES:
[231] [Greek: Pleios-morphosis].
CHAPTER I.
IRREGULAR PELORIA.
The term peloria was originally given by Linne to a malformation of
_Linaria vulgaris_, with five spurs and five stamens, which was first
found in 1742 near Upsal. This was considered so marvellous a
circumstance that the term peloria, from the Greek [Greek: pelor], a
prodigy, was applied to it.[232] After a time other irregular flowers
were found in like condition, and so the term peloria became applied to
all cases wherein, on a plant habitually producing irregular flowers,
regular ones were formed. The fact that this regularity might arise from
two totally different causes was overlooked, or at least not fully
recognised, even by Moquin-Tandon himself. Where a flower retains
throughout life the same relative size in its parts that it had when
those parts first originated the result is, of course, a regular flower,
as happens in violets and other plants. This kind of peloria may for
distinction sake be called regular or congenital peloria (see chapter on
that subject); but where a flower becomes regular by the increase in
number of its irregular portions, as in the _Linaria_ already alluded
to, where not only one petal is spurred, but all five of them are
furnished with such appendages, and which are the result of an irregular
development of those organs, the peloria is evidently not congenital,
but occurs at a more or less advanced stage of development. To this
latter form of peloria it is proposed to give the distinctive epithet of
irregular.
Peloria is either complete or incomplete; it is complete when the flower
appears perfectly symmetrical, it is incomplete when only a portion of
the flower is thus rendered regular. It is very common, for instance, to
find violets or Linarias with two or three spurs, and these intermediate
stages are very interesting, as they serve to show in what way the
irregularity is brought about. In _Antirrhinum_, _Linaria_, &c.,
intermediate forms show very clearly that it is to the repetition of the
form usually assumed by the petals of the lower lip that the condition
is due. This is also obvious in peloric flowers of the _Calceolaria_.
The perfect peloria of this flower is in general erect, with five
regular sepals, a regular corolla contracted at the base and at the
apex, but distended in the centre so as to resemble a lady's sleeve,
tight at the shoulder and wrist, and puffed in the centre!
[Illustration: FIG. 122.--Peloric flower of _Calceolaria_.]
Morren[233] describes a form intermediate between the ordinary
slipper-shaped corolla and the perfect peloria just described, and which
he calls sigmoid peloria. This flower is intermediate in direction
between the erect peloria and the ordinary reflected flower. The tube is
curved like a swan's neck and is dilated in front into two hollow
bosses, such as we see in the lower lip of an ordinary flower; beyond
these it is contracted and is prolonged into a slender beak terminating
in two hollow teeth, between which is the narrow orifice of the
corolla. The colour at the base of the tube inside is as in the perfect
peloria; while round the summit of the tube, in both cases, the
intensity of colour is greatest on the outside. Now, in a normal flower
the deepest colour is within just opposite the orifice of the corolla;
this deep colour is also seen outside of the central and most elevated
portions of the lower lip. In the peloria the deep colour at the base of
the tube represents that which is near the orifice under ordinary
circumstances, while the outer patch of colour at the apex corresponds
to that formed on the upper surface of the lower lip. On the other hand,
in peloric flowers of _Cytisus Laburnum_, _Clitoria Ternatea_,
_Trifolium repens_, and other Papilionaceae, it is the "standard," the
form of which is repeated. In the case of peloric aconites[234] the
lateral and sometimes the inferior coloured sepals assume the hooded
form usually peculiar to the upper sepal only, the number of the petals
or nectaries being correspondingly increased. Balsams become peloric by
the augmentation in the number of spurs.[235] So when orchids are
affected with irregular peloria it is the form of the labellum that is
repeated, the accessory lips being sometimes the representatives of
stamens, which are usually suppressed in these flowers,[236] but at
other times the appearance is due simply to the fact that all three
petals assume the form usually confined to the lip, the staminal column
being unaffected, except that its direction and relative position with
reference to the other parts of the flower is different from ordinary.
This was the case in some flowers of _Phalaenopsis equestris_ sent to me
by Mr. Wentworth Buller. Fig. 123 represents a flower of _Aristolochia
caudata_ with two lips, for which I am indebted to Mr. W. H. Baxter.
From these cases it is evident that the flowers in question become
regular by the repetition of the irregular parts.
[Illustration: FIG. 123.--Two-lipped flower of _Aristolochia caudata_.]
It is probable that peloria may occur in any habitually irregular
flower, and that, if more attention were directed to the subject,
illustrations might be obtained from a larger number of natural families
than can be done at present. It is, however, necessary to exercise
discrimination, and not to attribute to peloria all the cases that at
first sight appear to be so referable. Thus, Professor Dickson exhibited
at the Botanical Society of Edinburgh, December 13th, 1860, four
abnormal flowers of the common Indian cress (_Tropaeolum majus_), each
presenting a supernumerary spur. On these he remarked that "in
_Tropaeolum_ the posterior part of the receptacle between the insertion
of the petals and that of the stamens is dilated so as to form the spur
which is so characteristic in the genus. The position of the spur in a
line with the posterior sepal has led many botanists to consider it as a
process of that sepal, but the fact of its being situated within the
insertion of the petals is conclusive as to its receptacular origin. In
the flowers exhibited the supernumerary spur (as if to show its want of
connection with any sepal) was placed exactly between a lateral sepal
and one of the anterior sepals, sometimes on the one side of the flower
and sometimes on the other. These additional spurs were precisely
similar to the normal ones, except that they were a little shorter. This
abnormality, although at first sight seeming to indicate a pelorian
tendency, is no approximation to regularity, from the fact of the extra
spur being differently placed, with regard to the sepals, from the
normal one."
Peloria of this kind, when perfect, is very often associated with other
alterations. Change of direction is one of the most common of these; the
usually drooping flower becomes erect, the stamens and style also are
changed in direction, while, not unfrequently, either the one or the
other (most often the stamens) are entirely suppressed. With this
suppression an increase in the size of the flower very generally
coincides. The number of parts is also frequently increased; thus, in
_Antirrhinum majus_ the corolla, when subjected to peloria, is very
generally six-parted, and has six stamens. Fusion of one or more flowers
is also a common accompaniment of peloria, as in _Digitalis purpurea_,
in which plant prolification often adds increased complexity to the
flower.
It has been stated by Moquin and others that the uppermost flower of an
inflorescence is the most subject to peloria; the uppermost flower of
_Teucrium campanulatum_, for instance, is very generally regular. In
_Calceolaria_ it is the central terminal flower which is usually
peloriated; on the other hand, in _Linaria_ and _Antirrhinum_ the lower
flowers, or those on the secondary branches, are quite as often affected
as the primary ones. Cassini considered that the spur of _Linaria_ was
developed from the lower petal rather than from the upper ones, because
there is more room on the side of the flower farthest from the stem than
on the opposite side. With reference to this point, M. Godron remarks
that in habitually irregular flowers the apex of the peduncle is
oblique, and hence the flowers are bent downwards or spread
horizontally, but if the receptacle be quite flat and level then the
flower is regular. The oblique position causes some of the organs to
press on others, and hence induces abortion and suppression of some
parts and increased growth in others that are not subjected to pressure.
In a terminal peloriated flower of aconite, described by this
naturalist, the flower was removed so far from the nearest bracts that
all its parts had the chance of growing regularly. In ordinary cases M.
Godron considers that the compression of the lateral bracts is the cause
of the irregularity of the androecium and of the receptacle.[237]
It has also been somewhat too generally stated that peloria occurs
principally on luxuriant vigorous plants. It seems quite as often to
happen in plants characterised by their deficiencies in this respect. On
this point M. de Melicoq[238] says, referring to _Linaria vulgaris_
affected with peloria, that on the weakest plants the peloriated flower
was at the top of the stem; while in stronger plants, with more numerous
flowers and larger foliage, the peloriated flowers were principally to
be found in the centre and at the base of the inflorescence, and their
pedicels were much longer than usual.
Linne, as has been already stated, considered these flowers to be
sterile, and only capable of multiplication by division of the root, but
Willdenow obtained seeds from the _Linaria_ which reproduced the
anomaly when sown in rich soil. Baron Melicoq obtained similar
results.[239] Mr. Darwin[240] raised sixteen seedling plants of a
peloric _Antirrhinum_, artificially fertilised by its own pollen, all of
which were as perfectly peloric as the parent plant. On the other hand,
the same observer alludes to the tendency that these peloric plants have
to revert to the usual form, as shown by the fact that when the peloric
flowers were crossed with pollen from flowers of the ordinary shape, and
_vice versa_, not one of the seedlings, in either case, bore peloric
flowers. Hence, says Mr. Darwin, there is in these flowers "a strong
latent tendency to become peloric, and there is also a still greater
tendency in all peloric plants to reacquire their normal irregular
structure." So that there are two opposed latent tendencies in the same
plant. A similar remark has been made with reference to malformations in
general by other observers.
It would be very interesting if some competent naturalist would collect
information as to whether any variations in degree of fertility exist in
the three forms of flowers in _Linaria_, viz. the ordinary one-spurred
form, which is intermediate between the spur-less and the five-spurred
form. It must be remembered, however, that in the latter cases the
stamens are often deficient. In the _Compositae_, where there are regular
flowers in the disc and irregular ones in the ray, sexual differences,
as is well known, accompany the diversities in form.
To Mr. Darwin the author is indebted for the communication of some
flowers of _Corydalis tuberosa_ (figs. 124, 125), provided with two
spurs of nearly equal size. To these flowers allusion is made in the
work already quoted[241] in the following terms:--"_Corydalis tuberosa_
properly has one of its two nectaries colourless, destitute of nectar,
only half the size of the other, and therefore to a certain extent in a
rudimentary state; the pistil is curved towards the perfect nectary, and
the hood formed of the inner petals slips off the pistil and stamens in
one direction alone, so that when a bee sucks the perfect nectary the
stigma and stamens are exposed and rubbed against the insect's body. In
several closely allied genera, as in _Dielytra_, there are two perfect
nectaries; the pistil is straight, and the hood slips off on either
side, according as the bee sucks either nectary." In the flowers of
_Corydalis_, which were provided with two perfect nectaries containing
nectar, Mr. Darwin considers that there has been a redevelopment of a
partially aborted organ, accompanied by a change in the direction of the
pistil, which becomes straight, while the hood formed by the petals
slips off in either direction, "so that these flowers have acquired the
perfect structure, so well adapted for insect agency, of _Dielytra_ and
its allies."
[Illustration: FIG. 124.--Two-spurred flowers of _Corydalis_.]
[Illustration: FIG. 125.--Section through two-spurred flowers of
_Corydalis_, Magnified.]
Peloria, then, is especially interesting physiologically as well as
morphologically; it is also of value in a systematic point of view, as
showing how closely the deviations from the ordinary form of one plant
represent the ordinary condition of another; thus, the peloric
Calceolarias resemble the flowers of _Fabiana_, and De Candolle,[242]
comparing the peloric flowers of _Scrophulariaceae_ with those of
_Solanaceae_, concluded that the former natural order was only an
habitual alteration from the type of the latter. Peloric flowers of
_Papilionaceae_ in this way are indistinguishable from those of
_Rosaceae_. In like manner we may trace an analogy between the normal
one-spurred _Delphinium_ and the five-spurred columbine (_Aquilegia_),
an analogy strengthened by such a case as that of the five-spurred
flower of _Delphinium elatum_ described by Godron.[243] The _Corydalis_,
before referred to, is another illustration of the same fact, the
structure being the same as in _Dielytra_, &c.
The ordinary irregular flowers may possibly be degenerated descendants
of a more completely organized ancestor, and some of the cases of
peloria may therefore be instances of reversion; some ancient _Linaria_
may, perhaps, have had all its petals spur-shaped, and the cases of
irregular peloria now found may be reversions to that original form.
When both regular and irregular forms of peloria occur on the same
plant, as they frequently do in _Linaria_, the one may be perhaps
considered as a reversion to a very early condition, the other to a
later state, when all the petals were irregularly formed. But before we
can assert the truth of this surmise we must have better evidence as to
what the original condition really was than we have at present.
The proximate cause of irregular peloria has been considered to be
excess of nourishment, but evidence as to this point is very
conflicting. Willdenow states that "radices peloriae, solo sterili
plantatae, degenerant in Linariam," ('Sp. Plant.,' iii, p. 254); but this
opinion is counterbalanced by that of others, while the frequent
existence of both forms on the same plant, at the same time, seems to
negative the supposition of any direct effect from external
circumstances.
The following are the plants in which irregular peloria has been most
often observed:
Aconitum Napellus.
Delphinium elatum!
Corydalis tuberosa.
*Viola odorata!
hirta.
Impatiens Balsamina.
Clitoria Ternatea.
Cytisus Laburnum!
Trifolium repens!
Lupinus polyphyllus!
*Gloxinia, var. cult.!
*Linaria vulgaris!
spuria.
Elatine.
triphylla.
aeruginea.
triornithophora.
pilosa.
chalepensis.
cymbalaria!
purpurea!
decumbens.
Pelisseriana.
origanifolia.
Digitalis orientalis.
* purpurea!
Calceolaria crenatiflora.
rugosa.
* var. cult.!
Chelone barbata.
*Antirrhinum majus!
Rhinanthus crista galli.
Pedicularis sylvatica.
Pedicularis euphrasioides.
Scrophularia aquatica!
Sesamum indicum.
Lamium.
Mentha.
Sideritis.
Nepeta diffusa.
Galeopsis Ladanum.
Tetrahit.
Galeobdolon luteum.
Teucrium campanulatum!
Plectranthus fruticosus.
Cleonia lusitanica.
Dracocephalum austriacum.
Phlomis fruticosa!
Vitex incisa.
Aristolochia, sp.!
Ophrys aranifera!
Orchis simia.
pyramidalis!
latifolia!
morio!
papilionacea.
mascula.
latiflora.
conopsea.
Habenaria bifolia.
Corallorhiza innata.
Aceras anthropophora.
Cattleya Moasiae!
Phalaenopsis equestris!
Pogonia ophioglossoides!
The literature of peloria is very extensive. The following are the
principal papers, not already mentioned, which relate to the subject,
arranged under the genera, placing those first which are most subject to
this anomaly (see also Regular Peloria).
_Linaria_.--Adanson, 'Fam. Plant.,' t. i, p. 110. Jussien,
'Gen. Plant.,' p. 120. Poiret, 'Encycl. Method, Suppl.,' t.
iii, Jaeger, 'Missbilld. der Gewachs.,' pp. 94, 97, and 313.
Cassini, 'Op. Phytol.,' t. ii, p. 331. Ratzebourg, 'Animadv. ad
pelor. spectand.,' 1825. Turpin. 'Ic. Veget.,' tab. xx, f. 16.
Curtis, 'Flor. Londin.,' i, 118. Hopkirk, 'Flora Anom.,' pl.
vii, figs. 1, 2, 3. Haller, 'Act. Helvet.,' 2, p. 25, t. iv. De
Candolle, 'Flore Franc.,' t. iii, p. 583. Sowerby, 'Engl.
Bot.,' iv, 260, ed. Syme, tab. 963. Chavannes, 'Mon.
Antirrhin.' Delavaud, 'Bull. Soc. Bot. France,' 1858, p. 689;
id., 1860, p. 175. Heufler, 'Linnaea,' xvii, tab. ii. Weber,
'Verhandl. des Nat. Hist. Vereins. f. d. Rh. Preuss.,' 1850,
tab. i, figs. 1-8. 'Verh. Nat. Hist. Ver. Rh. Preus.,' 1849,
vol. vi, p. 290, tab. xiii.--_Antirrhinum_, Clos, 'Mem. Acad.
Toulous.,' vi, 1862. Chavannes, 'Mon. Antirrh.,' p. 62.
Fresenius, 'Mus. Senkenb.,' ii, t. iv, fig. 10. 'Bot. Soc.
Edinb.,' 1851, July 10.--_Calceolaria_, Chamisso, 'Linnaea,' t.
vii, p. 206. Guillemin, 'Archiv. Bot.,' t. ii, p. 1 et 136.
Schlechtendal, 'Linnaea,' xii, p. 686. Ernst Meyer, 'Linnaea,'
xvi, 26, tab. iii. Morren, 'Bull. Acad. Belg.,' t. xv, n. 7, et
t. xviii, p. 583. 'Gard. Chron.,' 1850, p. 389; ibid., 1866, p.
612.--_Viola_, Leers, 'Flor. Herborn.,' p. 145. De Candolle,
'Organ. Veget.,' t. i, p. 519, pl. xlv. Forbes, 'Proc. Linn.
Soc.,' June 6, 1848, p. 382. Hildebrand, 'Bot. Zeit.,' 1862,
vol. xx, tab. viii.--_Orchidaceae_, His, 'Jourl. Phys.,' 65, p.
241. Wydler, 'Arch. Bot.,' t. ii, p. 310, tab. xvi. R. Brown,
'Obs. organ. Orchid.,' p. 698. A. Richard, 'Mem. soc. d'hist.
nat.,' t. i, p. 212. Greville, 'Flora Edinens.,' p. 87
(_Corallorhiza_). Curtis, 'Flora Londinensis,' t. lxxxii.
Morren, C., 'Bull. Acad. Roy. Belg.,' t. xix, part ii, p. 171.
Clos, 'Mem. Acad. Sc. Toulous.,' 5 ser., vol. iii. Caspary,
'Schrift. K. Gesellsch. Koenigsberg,' 1860, i, 59. Masters,
'Jourl. Linn. Soc.,' vol. viii, p. 208 (_Ophrys_, _Pogonia_).
Duchartre, 'Bull. Soc. Bot. Fr.,' vol. vii, 1860, p. 26,
_Cattleya_. Cramer, 'Bildungsabweich.'--_Limosella_, Baillon,
'Adansonia,' i, p. 305. (Flower normally irregular, becoming
regular "a force d'irregularite.")--_Chelone_, Chamisso,
'Linnaea,' vii, p. 206,--_Clitoria_, Bonavia, 'Gard. Chron.,'
1868, p. 1013. In this latter communication, published as this
sheet is passing through the press, the author gives an
interesting account of the transitional stages between the
ordinary papilionaceous condition and the regular form which is
like that of a Rosaceous plant. The peloric form is stated to
be transmitted by seed.
For other references see Moq.-Tandon, 'El. Terat. Veget.,' p.
186. Hallier, 'Phytopathol.,' p. 151.
FOOTNOTES:
[232] 'Amoen. Acad.,' i, p. 55, t. iii (1744):--The following note
refers to Linne's notion that these forms were due to hybridization. It
is extracted from Gmelin's edition of the 'Systema Naturae,' 1791, p.
931. "_Linariae_ proles hybrida, ejusdemque qualitatis et constans,
radicibus infinite sese multiplicans charactere fructificationis
diversissima, corolla regulari, quinque-corniculata, pentandra, ut genus
proprium absolute constitueret et distinctissimum, nisi fructus
frequentissime abortiret. Naturae prodigium. Ita quidem a Linne.
Verisimilor autem videtur ea opinio, quae peloriam pro peculiari
degeneratione monstrosa floris habet, in quam inclinare hoc genus
(Linaria) prae aliis, similis a forma deflexio in aliis speciebus, e.g.
_spurio Elatine_, _cymbalaria_, observata, ... Merk., 'Goett. gel.
Anz.,' 1774, n. 121. Linck, 'Annal. Naturg.,' i, p. 32."
[233] 'Bull. Acad. Belg.,' xviii, part i, p. 591. Lobelia, p. 137.
[234] See also Seringe, 'Esquisse d'une Monogr. du genre _Aconitum_,' p.
124.
[235] Schlotterbec, 'Act. Helvet.,' t. ii, pl. i, Roeper. Balsam, p. 10,
note.
[236] Masters. "Peloria, &c., _Ophrys aranifera_," 'Journ. Linn. Soc.,'
viii, p. 207.
[237] Godron, "Mem. sur les Fumariees a fl. irreg.," 'Ann. Sc. Nat.,'
ser. 5, vol. ii, tab. xvii, p. 280.
[238] 'Bull. Soc. Bot. France,' vol. v, 1858, p. 701.
[239] 'Bull. Soc. Bot. France,' vol. vi, 1859, p. 717.
[240] 'Variation of Anim. and Plants,' ii, p. 70.
[241] Loc. cit., p. 59.
[242] 'Theor. Elem.,' ed. 2, p. 266.
[243] Cited in 'Bull. Soc. Bot. France,' vol. xiii (Rev. Bibl.), p. 81.
PART III.
METAMORPHY.
Much of the objection with which Goethe's famous essay on the
'Metamorphosis of Plants' was met on its publication may be traced to a
misapprehension of the sense in which Goethe employed the word. As used
by him, it had nearly the same signification as now applied to the word
development by organogenists. It does not necessarily imply that there
has been a change in any particular organ, but rather that there has
been, to some extent, a change in the plan of construction, in
accordance with which a deviation from the customary form results. The
particular organ was never anything else than what it is; it has not
been metamorphosed in the ordinary sense of the word; for instance, in a
double flower, where the stamens are, as it is said, changed or
metamorphosed into petals, no absolute change really has taken
place--the petal was never a stamen, although it occupies the position
of the latter, and may be considered a substitute for it.
The term metamorphosis, then, really implies an alteration in the
organizing force, taking effect at a very early period of the life of
the flower, at or before the period when the primitive aggregation of
cells, of which it is at that time composed, becomes separated or
"differentiated" into the several parts of the flower. In other words,
the "development" of the flower pursues a different course from what is
usual. In the preceding sections the effects of arrest and of excess in
this process have been partly treated of; other deviations arising from
similar causes will be mentioned elsewhere, but, under the present
heading, are specially included cases not of merely diminished or
increased, but of perverted development; the natural process is here not
necessarily checked or enhanced, but it is changed. Hence, in the
present work, the term metamorphy is employed to distinguish cases where
the ordinary course of development has been perverted or changed. As it
is applied solely for teratological purposes, the ordinary acceptation
of the term, as nearly synonymous with "development," is not interfered
with.
In order to avoid other possible misapprehensions, the terms retrograde
and progressive metamorphosis employed by Goethe are not herein used,
their place being, to a great extent, supplied by the more intelligible
expressions arrest or excess of development.[244]
FOOTNOTES:
[244] See Goethe, 'Versuch. der Metam. der Pflanzen,' 1790. English
translation by Emily M. Cox, in Seemann's 'Journal of Botany,' vol. i,
1863, p. 327. For a brief sketch of the origin and progress of the
theory of vegetable morphology, prior to the publications of Wolff,
Linne, and Goethe, as well as for an attempt to show what share each of
these authors had in the establishment of the doctrine, the reader is
referred to an article in the 'Brit. and For. Medico-Chirurgical
Review,' January, 1862, entitled "Vegetable Morphology: its History and
Present Condition," by Maxwell T. Masters.
CHAPTER I.
PHYLLODY.
This condition, wherein true leaves are substituted for some other
organs,[245] must be distinguished from Virescence, q. v., in which the
parts affected have simply the green colour of leaves, without their
form or structure. The appearance of perfect leaves, in place of other
organs, is frequently looked on as due to retrograde metamorphosis, or
to an arrest of development. But this is not strictly correct; for
instance, suppose a petal, which is very generally merely the sheath of
a leaf, with the addition of colouring matter, to be replaced by a
perfect leaf, one in which all three constituent parts, sheath, stalk,
and blade, are present, it surely can hardly be said that there has been
any retrogression or arrest of development in the formation of a
complete in place of an incomplete organ. The term retrograde here is
used in a purely theoretical sense, and cannot be held to imply any
actual degradation. Morphologically, as has been stated, the case is one
of advance rather than the reverse, and hence the assignment of
instances of this nature to a perversion of development, rather than to
a diminution or to an exaltation of that process, seems most consistent
with truth. The affected organs have really undergone no actual change,
simply the direction of the organising force has been altered at a very
early state, so that the usual differentiation of parts has not taken
place.
[Illustration: FIG. 126.--'Rose plantain,' _Plantago media var._, spike
contracted; bracts leafy.]
=Phyllody of the bracts.=--As bracts are very generally imperfect
organs, so their replacement by perfect leaves is not attributable to
arrest of development or retrograde metamorphosis, but the reverse. The
bracts of some species of _Plantago_[246] are very subject to this
change. Thus, in the rose plantain of gardens, _P. media_ (fig. 126),
the bracts are leafy and the axis depressed or not elongated, so that it
is surmounted by a rosette of small leafy organs. A similar condition of
the bracts, unattended with arrest of growth in the axis, is common in
_P. major_ (fig. 127) and in _P. lanceolata_ (see p. 108). It also
occurs in the bracts of _Corydalis solida_, _Amorpha fruticosa_, _Ajuga
reptans_, _Parthenium inodorum_, _Centaurea Jacea_, in the involucral
bracts of the dandelion, the daisy, and many other composites. In the
'Gardeners Chronicle,' 1852, p. 579, is figured a dahlia in which the
bracts of the involucre and the scales of the receptacle had all assumed
the form, texture, and venation of leaves.[247]
[Illustration: FIG. 127.--Leaf-like bracts in _Plantago major_.]
[Illustration: FIG. 128.--Dahlia. Scales of receptacle leafy.]
In _Umbelliferae_ the substitution of leaves for involucral bracts is not
infrequent. It has been observed among other plants in _Angelica
Razoulzii_, _Carum carui_, _Daucus Carota_, &c. The scales of the hop
(_Humulus Lupulus_) not infrequently manifest this change, as do also
the bracts of many amentaceous plants, _e.g._ in the male catkins of
the walnut, the female catkins of the alder,[248] of some willows,[249]
&c. The bracts of some _Euphorbiaceae_, as _E. pusilla_, _E. Lathyris_,
_E. Cyparissias_, have been observed to undergo a similar
alteration.[250]
Amongst monocotyledons an analogous change occurs not unfrequently, as
in some commelynaceous plants, _e.g._ _Tradescantia_, in _Musa_, &c.
The spathe of _Arum maculatum_ is sometimes represented by a stalked
leaf similar to that which occurs, under ordinary circumstances, in
_Spathiphyllum_, but in which genus the spadix is more or less adherent
to the leaf-like spathe.[251] In _Schoenus cephalotes_ a similar
exaggerated development of the bracts is figured by Rottboell.[252]
=Phyllody in inflorescence of Conifers.=--This demands passing notice by
reason of the interest attaching to the morphological construction of
these plants. The elongation of the axis which occurs in the female
cones has been already alluded to under the head of prolification of the
inflorescence. This change is frequently associated with a more or less
foliaceous condition of the bracts, which, indeed, may be seen to be
serially continuous, both above and below, with the ordinary leaves. The
scales, too, become notched and bipartite, and show, between the lobes,
the rudiment of a bud, which in a further stage becomes developed into a
shoot bearing leaves. Such a change has been described by Parlatore in
_Abies Brunoniana_, and examples may frequently be met with in the larch
(_Larix europaea_), and specially in _Cryptomeria japonica_.[253] The
scales of the male catkins of conifers likewise occasionally assume the
appearance of leaves; this may be seen in monstrous catkins of
_Araucaria_, as also in _Podocarpeae_ and _Cupressineae_ (Eichler).
=Phyllody of the calyx.=--Sepals under ordinary circumstances are so
like leaves, that it is not wonderful that they are often replaced by
those organs.[254] A singular instance of this has been mentioned as
occurring in _Cakile maritima_, wherein the sepals were found by M.
Fournier to be pinnatifid like the ordinary leaves of the plant.[255]
The sepals of _Ranunculaceae_ and _Rosaceae_, for example, _Rosa_, _Geum_,
are particularly liable to this change.
[Illustration: FIG. 129.--Flower of rose, sepals replaced by five
perfect leaves; axis prolonged through the flower in the form of a leafy
branch.]
In a species of _Geranium_ recently examined the sepals presented
themselves in the form of three-lobed leaflets; so in fuchsias and in
_Epilobium hirsutum_ the sepals occasionally are not distinguishable
from ordinary leaves (fig. 130). In roses, the change in question is a
very frequent accompaniment of prolification (fig. 129). In the peach
also this replacement of the sepals is sometimes carried to such an
extent, that five perfect, bistipulate leaves occur in the place of the
calyx, but when this is the case it usually happens that the pistil is
abortive.
[Illustration: FIG. 130.--Fuchsia, with one of the sepals leaf-like.]
De Candolle[256] figures a curious instance wherein the pappus of
_Podospermum laciniatum_ was replaced by five linear, foliaceous lobes.
A similar change has been noticed in other composites, as in _Tragopogon
pratense_. Engelmann mentions as subject to this hypertrophy of the
pappus, as it may be termed, _Scorzonera octangularis_ and _Senecio
vulgaris_. Wigand has observed a similar transformation in a species of
_Centranthus_ (_Valerianaceae_).
In some cases the phyllody of the sepals has a special interest, as
bearing on the question whether what is termed calyx-tube is or is not a
portion of the calyx, and whether the sepals are modifications of the
blade or of the sheath of the leaf. Thus in the primrose the phyllodic
sepals seem to show clearly that the sepals are in that plant of a
laminar nature (fig. 131). The so-called calyx-tube of roses is
elsewhere alluded to. The leaf-like organs sometimes seen at the apex of
a cucumber would seem to support the view that there was really a
calyx-tube in _Cucurbitaceae_ adherent to the carpels. It is also shown
in the cut, fig. 132, borrowed from the 'Gardeners' Chronicle,' 1859,
p. 654.
[Illustration: FIG. 131.--Primrose. Calyx of foliaceous segments.]
[Illustration: FIG. 132.--Leafy calyx of melon.]
Under ordinary circumstances, the sepals may be considered as the
representatives of the sheath of the leaf (cataphyllary) or of the blade
(euphyllary), the arrangement of the veins being different in the two
cases; thus, in the vagina or sheath, there are generally several large
veins of about equal size, either convergent towards the apex, or
divergent; on the other hand, in the blade, there is usually but one
central vein, the midrib, larger than the rest, and the smaller veins
come off at a less acute angle, and are more reticulated.[257]
Now, when phyllomorphy occurs in sepals which ordinarily are vaginal, it
is obvious that the case is one, not merely of increased relative
growth, but also of the appearance or development of an organ habitually
suppressed; on the other hand, when phyllomorphy occurs in sepals which
usually are laminar in form and nervation, the case is one of unusual
growth or hypertrophy, and not of the development of an organ habitually
suppressed, so that the amount of change is greater in the former than
in the latter instance.
Under normal circumstances it will be found that laminar venation is
most common in gamosepalous and vaginal venation in polysepalous
calyces. And the same holds good in cases where the calyx is abnormally
leafy. The complete leaf development shows itself more frequently among
the monosepalous plants than in the polysepalous ones, as shown even in
the subjoined list of species. This statement would be more fully
verified were it possible to state the frequency with which the
condition occurred in _individual plants_, when it would be found that
phyllody of the calyx occurs much more often in individual gamosepalous
plants than in polysepalous ones.
Phyllody of the calyx has been most often observed in the following
plants:
Ranunculus acris!
Delphinium Ajacis.
Caltha palustris.
Anemone Pulsatilla.
sylvestris!
nemorosa!
hortensis!
coronaria!
*Papaver orientale.
Escholtzia crocea.
Cakile maritima.
Diplotaxis tenuifolia.
Thlaspi arvense.
Cheiranthus Cheiri.
incanus.
Sinapis arvensis.
Brassica oleracea!
Peltaria alliacea.
*Sisymbrium officinale.
Caryophyllaceae,[258] sp. pl.
Geranium, sp.!
*Fuchsia, var. hort.!
Epilobium hirsutum!
Cucurbita Pepo!
*Rosa, var. hort.!
Potentilla nepalensis.
Fragaria sp.
Geum rivale.
Amygdalus communis.
Persica vulgaris.
Cerasus!
Pyrus Malus.
Daucus Carota.
Athamanta Cervaria.
*Trifolium repens!
Centranthus macrosiphon.
Tragopogon pratense.
orientale.
Scorzonera octangularis.
Hypochaeris radicata.
*Senecio vulgaris!
Podospermum laciniatum.
Cirsium arvense.
Carduus heterophyllus
tataricus.
Campanula, sp.
Convolvulus sepium.
*Primula officinalis, var. cult!
acaulis.
elatior.
Gentiana campestris.
*Petunia violacea!
Lycium europaeum.
Laurus Sassafras.
Tulipa Gesneriana.
Convallaria maialis.
Colchicum autumnale! (virescent?)
Consult also Turpin, 'Atlas de Goethe,' t. iv, f. 12, _Lycium_.
Engelmann, 'De Anthol.,' Sec. 35, p. 31. This author figures
phyllodic sepals in _Senecio vulgaris_, tab. v, figs. 24-26;
_Campanula_, tab. iii, f. 15, 16; _Athamanta cervaria_, tab. v,
f. 14. Lindley, 'Elements of Botany,' 1847, pp. 64, 73, &c.
'Gard. Chron.,' 1858, p. 685; 1859, p. 654, _Cucurbita_.
Petunnikoff, 'Bull. Soc. Imp. Moscow,' 1862, _Cirsium_. Braun,
'Rejuvenescence,' Ray Society's Transl. See succeeding
paragraphs.
=Phyllody of the corolla.=--The petals also are frequently replaced by
leaves, though in many of the recorded instances the change has been one
of colour only; these latter are strictly cases of virescence. M.
Seringe[259] speaks of a flower of _Peltaria alliacea_ in which the
calyx was petal-like, while the corolla was leafy as if there had been
transposition of the two organs, a very rare, if not unparalleled,
instance. In a flower of _Campanula Medium_, provided, as is often the
case, with a double corolla, the outer corolla was slit down on one
side, the edges of the cleft being leafy.
[Illustration: FIG. 133.--Sepals and petals to leaves. _Geranium_.]
The frondescent petals are very often completely disjoined, as in
_Verbascum nigrum_, and _Lonicera Periclymenum_, in which, moreover,
median prolification generally coexists. In the case of _Tropaeolum
majus_, the ordinary leaves of which are peltate and orbicular, the
petals when frondescent have not the peltate arrangement, but are
spathulate, and provided with very long, narrow stalks, so that, in some
cases, they are, more properly speaking, enlarged virescent petals than
true leaves; in other instances, however, the arrangement of the veins
is more like that of the true leaves than that of the petals.
As might be expected, frondescence of the petals is frequently
accompanied by other changes of a similar nature in other parts of the
flower, and sometimes by the abortion of the sexual organs. Thus, in
_Actaea spicata_, as observed by Fresenius, the petals were replaced by
true petiolate, palminerved, lobed leaves, the stamens and pistils
being abortive. In _Ranunculus_ the leaves that appear in the place of
the petals have no scale at their base, and in _Tropaeolum_ the calyx (or
receptacle) is free from the usual spur.
The absolute frequency of this occurrence seems to be greatest in those
flowers which are normally polypetalous. The petals of these flowers, as
a general rule, are more like the leaf-sheaths than the leaf-blades as
to their venation, hence it would seem that the phyllomorphic condition
in these petals is a manifestation of a greater degree of organizing
force than that which occurs in those cases where the petals are
normally present in the form of contracted blades or laminae. (See the
remarks in the preceding section.)
Frondescence of the petals has been observed most frequently in the
following cases; some, perhaps, were cases merely of virescence, q. v.;
see also under Chloranthy, Prolification.
Ranunculus repens!
Delphinium Ajacis.
crassicaule.
Aquilegia vulgaris.
Actaea spicata.
*Brassica oleracea!
Diplotaxis muralis.
Hesperis matronalis.
Thlaspi bursa pastoris.
Sisymbrium tenuifolium.
Turritis glabra.
Raphanus sativus.
Peltaria alliacea.
Alyssum incanum.
Erysimum Barbarea.
officinale!
cheiranthoides.
Cheiranthus Cheiri.
*Dictamnus Fraxinella!
Lychnis sylvestris.
dioica!
Alsine media.
Cerastium vulgatum!
triviale.
Reseda lutea.
Phyteuma.
Malva sylvestris.
*Tropaeolum majus!
Geranium, sp.!
Triumfetta, sp.!
Epilobium hirsutum!
OEnothera striata.
Rubus, sp.
*Rosa, var. cult.!
*Trifolium repens!
Spiraea oblongifolia.
Amygdalus communis.
*Rosa!
Cerasus vulgaris!
Persica vulgaris!
Potentilla nepalensis.
Geum rivale.
Daucus Carota!
Heracleum Sphondylium.
Torilis Anthriscus.
Echinophora maritima.
Campanula rapunculoides.
glomerata.
Phyteuma spicatum.
Calendula officinalis.
Cirsium tricephalodes.
Senecio vulgaris.
Scabiosa columbaria.
agrestis.
Lonicera xylosteum.
Periclymenum.
Gentiana Amarella.
Gilia glomeriflora.
*Symphytum officinale.
Petunia violacea!
Verbascum, sp.
Antirrhinum majus!
Stachys sylvatica.
*Anagallis phoenicea?
Primula sinensis!
Polemonium coeruleum.
See Moquin-Tandon, 'El. Terat. Veg.,' p. 203. Engelmann, 'De
Anthol.,' Sec. 38 _et seq._; tab. ii, figs. 8-14, _Gilia_; tab.
v, 23-26, _Senecio_; tab. v, f. 1-13, _Torilis_; tab. iv, f. 3,
_Erysimum_. 'Bull. Soc. Bot. Fr.,' vol. ii, 1855, p. 479,
_Primula sinensis_. Giraud, 'Edinb. Phil. Magazine,' 1839,
_Antirrhinum_. Jaeger, 'Act. Acad. Caes. Nat. Cur.,' vol. xiii,
2, p. 1, tab. xli, _Tropaeolum_. Bischoff, 'Lehrbuch,' 11, 2, p.
27, _note_, _Tropaeolum_. Fresenius, 'Mus. Senkenb.,' ii, 35,
tab. 4, fig. 5, _Actaea_. See also succeeding paragraphs and
sections in Chloranthy, Virescence, &c.
=Phyllody of the stamens= happens less frequently than the corresponding
condition in the neighbouring organs. The structure of the anther is so
much removed from that of the leaf, that the change of the stamen from
its ordinary condition to that of a leaf must be regarded as indicating
a greater degree of perverted development than that which occurs in
those cases where less highly differentiated organs, such as the sepals,
petals, and pistils, are thus altered.[260]
In all cases it is desirable to ascertain, if possible, what parts of
the stamen are thus transformed. In some Petunias the filaments are
unchanged, but in place of the anther is a small lamina, representing
precisely the blade of an ordinary leaf. Sometimes the connective only
is replaced by a leaf. One of the most interesting cases of this kind
that has fallen under the writer's observation was in _Euphorbia
geniculata_, in which, in addition to other changes mentioned under
prolification of the inflorescence, some of the stamens were partly
frondescent, half the anther being perfect, the other half leaf-like.
Another filament bore just above the usual joint three leaflets, two
lateral ones, somewhat conduplicate, and a third central one, half
anther, half leaflet.
[Illustration: FIG. 134.--Flower of a _Petunia_, opened to show the
stamens partially replaced by stalked leaves.]
In the case of frondescent flowers of _Tropaeolum majus_ the stamens are
usually absent or atrophied, but in other instances the filament is
present as usual, representing the stalk of the leaf, and surmounted by
a small lamina, but this latter, in place of being nearly flat, is
pinched up in the centre from back to front, and surmounted by a
two-lobed anther, so that the general appearance of the whole structure
is that of a central anther, supported at the base on each side by two
concave leaf-lobes, or it might be compared with a three-lobed leaf, the
terminal lobe represented by the anther.
In _Jatropha Pohliana_, Muell. (_Adenorophium luxurians_, Pohl.), a
singular condition has been observed by M. Mueller (Argov.). In this
flower the anther, in place of being represented by the flat blade of a
single leaf, had the appearance as if two such blades were present and
coherent one with the other by their midribs, along their upper or inner
surfaces, which were directed towards the centre of the flower (fig.
136), thus resembling the cases of adhesion of leaves by their surfaces
already referred to (p. 33). In other cases, in the same plant, the
anther appeared as if formed by two collateral leaves, the faces looking
towards the circumference of the flower, and their margins so folded
together as to represent an open anther lobe (fig. 135). These cases are
apparently due, not to the formation and adhesion of two leaves, but
rather to the exuberant development of one leaf into two blades.[261]
The bearings of these and other similar malformations on the morphology
of the anther are alluded to under the head of petalody of the anther.
[Illustration: FIG. 135.--Phylloid anther of _Jatropha_, after Mueller
(Arg.).]
[Illustration: FIG. 136.--Leaf-like anther of _Jatropha Pohliana_, after
Mueller.]
Phyllody of the stamens has been most often observed in the following
plants:
Anemone nemorosa.
coronaria.
Delphinium crassicaule.
Nymphaea dentata.
Tropaeolum majus!
Dictamnus albus.
*Trifolium repens!
Torilis anthriscus.
Heracleum Sphondylium.
Daucus Carota
Epilobium hirsutum!
*Rosa, var. cult.!
Lonicera Periclymenum.
Anagallis arvensis.
Primula sinensis!
Petunia, var. cult.
Jatropha Pohliana.
Euphorbia goniculata.
In addition to the foregoing there are very numerous instances of
similar substitution in chloranthic flowers. In the above list only
those cases are given wherein the leafy change is confined to the
stamens, or, at least, to a few only of the other parts of the flower.
=Phyllody of the pistils.=[262]--This is of more common occurrence than
is the corresponding change in the case of the stamens. It is of
interest, as it sometimes serves to illustrate the morphological nature
of the pistil. Of this the double-flowering cherry is a well-known
illustration, the pistil being here represented by two small foliar
laminae, whose midribs are prolonged with a short style, terminated by an
imperfect stigma. It is usually the basal portion of the pistil, the
ovary, which is thus specially affected, the margins being also often
disunited so as to expose the ovules. These latter organs may be absent
or they may themselves be the subjects of foliaceous development.
Moquin[263] relates having found in the neighbourhood of Montpellier a
flower of a tulip the ovary of which was represented by true leaves,
which bore on their margins the ovules, and thus presented a striking
analogy with the carpels of those Sterculias, like _S. platanifolia_,
which are foliaceous in texture and open very early in the course of
their development. A similar occurrence has also been frequently
noticed in the Columbine and also in _Cruciferae_ and _Umbelliferae_. M.
Germain de St. Pierre mentions an instance wherein the carpels of _Salix
Babylonica_ were converted into two leaves, provided with stipules. All
the flowers of the catkins were similarly changed, so that it became
permanent, and resembled a branch.
[Illustration: FIG. 137.--Rose, in which the axial portion of the flower
was elongated and the carpels were more or less replaced by leaves.]
Substitutions of this kind form the green "eyes" or centres of certain
varieties of _Ranunculus_ and _Anemone_.
In proliferous roses, or in cases where the central axis of the flower
is prolonged, it frequently happens that the pistils are more or less
replaced by leaves. Fig. 137, from a specimen of Dr. Bell Salter's,
given in the 'Gardeners' Chronicle,' shows the passage, from below
upwards, of the ordinary carpels to perfect leaves; the so-called
calyx-tube being completely deficient and the ovaries entirely superior.
Like most similar specimens, this one bears out the notion that what is
called the calyx-tube in roses is really an expansion and dilatation of
the top of the flower-stalk.
[Illustration: FIG. 138.--Cucumber with leaf attached.]
Fig. 138, for which I am indebted to Mr. S. J. Salter, represents a very
singular conformation in the cucumber, described by that gentleman in
'Henfrey's Botanical Gazette,' i, p. 208, and considered by him to be
due to the foliaceous condition of one of the three carpels of which the
fruit is composed. The portion near the peduncle was binary, while the
distal extremity of the fruit was ternary. The main difficulties
attending the acceptance of this explanation reside in the peculiar
reversed position of the leaf, and in the fact that the fruit of the
_Cucurbitaceae_ is probably of axial nature, the dilated and succulent
end of the peduncle adhering to and usually concealing the carpels; in
some cases, however, these latter project beyond the axial portion,
leaving no doubt as to the true nature of the structure in these
particular instances.
Admitting the axial nature of the fruit, it might be supposed that in
Mr. Salter's cucumber an adventitious leaf had been given off from the
axis, but even on that supposition the reversed position offers a
difficulty, and there still remains to be explained the fact that the
proximal part of the fruit was binary in its constitution, the distal
end ternary.
M. Norman[264] mentions a case wherein the carpels of _Anchusa
ochroleuca_ were replaced by two leaves; from this he draws the
inference that the pistil of borages and labiates is really composed of
two leaves, placed fore and aft, the margins of the leaves being
congenitally fused. This tallies well with the account given of the
development of these plants by Payer, Germain de St. Pierre, and others.
In an Indian species of _Triumfetta_, not only were the petals
virescent, but the ovary also was much enlarged, and in some flowers it
was divided half way down into five lanceolate leaves (fig. 139), the
sepals and stamens being in their normal condition.
In the preceding instances the foliaceous condition has pervaded the
entire pistil, or at any rate the basal portion or ovary, and it may be
noticed that the ovary is thus shown to consist in some cases of the
sheath of the leaf, as in _Aquilegia_; in other cases of the blade, as
in _Cerasus_, _Daucus_, &c.
[Illustration: FIG. 139.--Flower of _Triumfetta_, sp., carpels
represented by five leaves.]
There are cases, however, in which a part only of the pistillary
structure thus becomes foliaceous. Linnaeus, 'Prolepsis,' Sec. 9,
mentions some flowers of _Carduus heterophyllus_ and _C. tataricus_ in
which the style had grown into two green leaflets, and in which the calyx
and corolla were also leaf-like. A very singular instance is recorded by
Baillon,[265] wherein the pistil of _Trifolium repens_ consisted of
three carpels, either separate, or combined so as to form a one-celled
ovary with three parietal, pluri-ovulate placentae; the ovary in these
flowers was formed of the basal vaginiform part of the leaf; the three
styles were formed by the petioles, while the stigmas were represented
by trifoliolate leaves. The back of the leaf in these cases is usually
directed away from the centre of the flower. When this change occurs it
is commonly attended by an increased number of parts, as in the trefoil
just mentioned, or in the double cherry, where usually two foliaceous
carpels may be met with, and sometimes more.
The change is also of interest when it affects such orders as the
_Umbelliferae_, which have their ovaries inferior under ordinary
circumstances; but when these organs assume a leafy condition they
become superior also, _i.e._ they are detached from the calyx.
As regards the position of the ovules in these foliaceous pistils, they
may be placed, as in _Aquilegia_, _Delphinium_, &c., on the edges of the
carpel or on the surface, as in some flowers of _Ranunculus repens_ and
_R. Ficaria_. A similar position of the ovules is recorded in the case
of the vine (_Vitis_), where the pistil consisted of leaves bearing the
ovules on their inner surface.[266] The supposed causes of this and
other similar malformations are alluded to under the head of chloranthy,
but it may be here remarked that semi-double flowers, fertilised by the
pollen of similar flowers, are said to produce flowers with a centre of
small green leaves, this central tuft resulting from the expansion and
frondescence of the pistils.
As this condition rarely occurs without corresponding changes in other
parts of the flower, further remarks on this subject will be found in
the chapter relating to Chloranthy.
Phyllody of the pistil has been most frequently recorded in the
following plants:
Paeonia officinalis.
Ranunculus repens!
*Aquilegia vulgaris!
Delphinium elatum.
crassicaule.
Ajacis.
amaenum.
Nymphaea dentata.
Sinapis arvensis!
Diplotaxis tenuifolia.
*Brassica oleracea!
*Sisymbrium officinale!
Dianthus. sp
Reseda Phyteuma.
Triumfetta, sp.!
Lychnis dioica.
Cerastium, sp.!
*Dictamnus Fraxinella!
Cerasus avium.
vulgaris!
*Rosa, var. cult.!
*Daucus Carota!
Heracleum, sp.
Epilobium hirsutum!
Lathyrus latifolius.
*Trifolium repens!
hybridum.
Melilotus, sp.
Medicago, sp.
Lonicera Periclymenum.
Carduus heterophyllus.
tataricus.
Scrophularia aquatica.
Symphytum officinale.
Anchusa ochroleuca.
paniculata.
*Primula sinensis!
Salix babylonica.
Hyacinthus, sp.
Tulipa, sp.
Some of the above are probably cases of mere virescence rather than of
phyllody. For further illustrations, references to authorities, &c., see
under Chloranthy, Virescence, Prolification, &c.
=Phyllody of the ovules.=--Pending the settlement of the existing
differences of opinion with reference to the morphological nature of the
ovule and its component parts, much interest attaches to the
malformations to which they are occasionally subject. Considered purely
in a teratological point of view, it seems clear that the ovular coats
are usually, if not always, of foliar nature, while the central nucleus
is an axial organ; but if this be so there still remains the question
whether the leafy coats of the ovule are processes of the carpel itself,
or distinct independent formations, like the scales of a leaf-bud; as to
this latter point, the evidence is at present very conflicting. Prof.
Al. Braun, who has devoted much attention to the subject, describes and
figures ovules of _Nigella_ and _Adonis_, wherein the outer coat of the
ovule was converted into a leafy, lobed mass, like the ordinary leaves,
and these he considers to be a portion, not of the carpel, but of the
ovular bud; he, however, hesitates to pronounce an opinion on the nature
of the pedicel of the ovule. In _Primulaceae_, wherein ovular changes are
very common, the leafy coat of the ovule would seem, from the nature of
the placenta, to be independent of the carpel. Morren, who studied the
changes in the ovules of _Primula sinensis_, applied the term
lepyrophylly ([Greek: lepyron], a scale) to the foliaceous condition of
the testa in this plant. Unger[267] describes a series of malformations
in _Primula sinensis_, consisting chiefly of reversions of the part of
the flower to leaves. The carpels were entirely absent in this case, and
the place of the free central placenta was occupied by a circle of
leaves, sometimes bearing imperfect ovules on their edges. An instance
of a similar kind has been described by A. de Candolle.[268]
In these flowers the placenta seemed to be composed of several funiculi
soldered together, and bearing imperfect ovules. In other cases no
traces of ovules are visible, but the funiculi are in a foliaceous
condition. Moquin also alludes to a case of the same nature in _Cortusa
Mathioli_, in which the funiculi bore little rounded leaves. Brongniart
has described some malformations of _Primula sinensis_ in which the
ovules were transformed wholly or partially into small leaves with three
to five lobes.[269] Dr. Marchand[270] mentions similar changes in
_Anagallis arvensis_ and _Lonicera Periclymenum_.
Cramer[271] figures ovules of _Primula sinensis_ in the form of stalked
leaves, often becoming infolded at the margins, and giving origin to a
small nucleus on their inner surface.
M. Tassi[272] records an instance in _Symphytum officinale_ wherein the
ovules were replaced by two small linear leaves arising entirely from
the axis, and not from the carpels.
In most of the foregoing illustrations the foliar portion of the ovule
must have been independent of the carpel; this independence is less
manifest, though probably as real in the cases now to be mentioned. In
_Sinapis_ and in _Brassica oleracea_ foliaceous ovules may occasionally
be seen, attached to the placenta by long stalks. No trace of the
nucleus is visible in these specimens.
[Illustration: FIG. 140.--_Sinapis_, replum and ovules; the dotted line
shows the position of the carpels.]
Griffith, in alluding to a similar case in _Sinapis_,[273] describes the
ovules as foliaceous, and having their backs turned away from the axis,
the raphe being next to the axis and representing the midrib the funicle
corresponding to the petiole. The outer tegument of the ovule, according
to Griffith, is a leaf united along its margins, but always more or less
open at its apex. No inversion can, therefore, really take place in
anatropous ovules, but the blade of the leaf is bent back on the
funicle, with which its margins also cohere.
Caspary, in an elaborate paper on phyllomorphy occurring in _Trifolium
repens_, figures foliaceous ovules springing from the edge of an open,
leafy carpel. The nucleus of the ovule, in these cases, appears to
originate as a little bud from the surface of the leafy ovule (figs.
141, 142).
[Illustration: FIG. 141.--Leafy ovules, &c., _Trifolium repens_.]
In a species of _Triumfetta_ (see p. 260), of which I examined dried
specimens, the ovary was open and partly foliaceous; it bore on its
infolded margins ten erect leaflets, representing so many ovules; each
leaflet was conduplicate, the back being turned towards the placenta.
[Illustration: FIG. 142.--Leafy ovules of _Trifolium repens_, showing
formation of nucleus, &c. After Caspary.]
On the other hand, there are cases in which the leafy coat of the ovule,
in place of being a distinct organ, seems to originate from the margin
of the carpellary leaf itself--to be, as it were, a lobule or small
process of the carpel, and not an absolutely new growth. Thus,
Planchon[274], from an examination of some monstrous flowers of _Drosera
intermedia_, was led to the inference that the ovules are analogous to
hairs on the margins of the leaves. This acute botanist was enabled to
trace all the gradations between the simple cup formed by the
confluence of four glanduliferous hairs and the concave leaf and the
perfect ovule.
Brongniart[275] records ovules of _Delphinium elatum_ existing in the
form of marginal lobes of the carpellary leaf itself; so that each ovule
corresponds to a lobe or large tooth of this leaf, the funiculus, as
well as the raphe, being formed by the median nerve of the lateral lobe.
M. Clos[276] mentions a similar instance in _Aquilegia Skinneri_; and
another is figured in Lindley's 'Elements of Botany,' p. 88, f. 180.
[Illustration: FIG. 143.--Portion of an open foliaceous carpel of
_Delphinium_, with ovules on the lobules.]
Cramer[277], from an examination of several ovular malformations, as
well as from the investigation of the mode of evolution of the ovules,
is led to a similar conclusion with reference to the production of
ovules from the modified lobes of the carpellary leaf. Figs. 143-145,
copied from Cramer, show how the nucleus of the ovule is formed as a new
growth from the surface of the lobes of the leaf in _Delphinium elatum_.
[Illustration: FIG. 144.--Section through marginal lobe of carpel
(_Delphinium_), showing the nucleus (_n_).]
[Illustration: FIG. 145.--Section through marginal lobe of carpel,
showing nucleus and tegument (_Delphinium_).]
[Illustration: FIG. 146.--1. Placenta of _Dianthus_, bearing ovules and
carpels. 2. One of the ovaries separated.]
[Illustration: FIG. 147.--Ovules of _Dianthus_ passing into carpels.]
One of the most singular instances of ovular malformation in record is
that cited by the Rev. M. J. Berkeley, in the 'Gardener's Chronicle,'
September 28th, 1850, p. 612. The plant was a carnation, and its
placenta bore, not only ovules, but also carpels (fig. 146), the latter
originating in a perverted development of the former, so that many
intermediate stages could be traced between the ordinary ovule and the
ovary (fig. 147, 1, _a_, 2, _b_). Some of these carpels, thus derived
from the ovules, themselves bore secondary ovules on a marginal
placenta, as shown in the sections at _c_, _d_, _e_. Could such a change
occur in the animal kingdom, there would be the unfertilised ovum
converted into an ovary, and this again bearing Graafian vesicles! In
Mr. Berkeley's carnation the change was not so great, seeing that the
nucleus of the ovule was not developed, and sufficient evidence has been
above given as to the foliar nature of the primine, while for a leaf to
be folded up so as to form a carpel is an ordinary occurrence.
It is worthy of remark that in these foliaceous ovules there is never
more than one coat, the secondine and other integuments do not make
their appearance in these cases, and that very generally the change in
question accompanies a similar foliaceous condition in the carpel, the
margins of which are more or less disunited.
Prof. A. Braun remarks that up to this date no such change has been
observed in the ovules of Monocotyledons.
=Changes in the nucleus of the ovule.=--The preceding remarks have had
reference especially to the ovular coats, but it is desirable also to
allude to certain points connected with the nucleus. Very frequently,
when the coat of the ovule is phylloid, as before described, the nucleus
is altogether wanting, though sometimes it is present as a small
cellular papilla; very rarely is it to be found in its perfect state.
Occasionally the nucleus is present in the guise of a small elongated
branch. Wigand cites ovular buds in every stage of progress into a
branch, sometimes even bearing indications of anthers. Wydler has
observed a similar occurrence in ovules of _Alliaria officinalis_, and
Schimper has described and figured specimens of _Nigella damascena_ in
which the outer coats of the ovule were but little changed, while the
nucleus was replaced by a leafy shoot. On one of the leaves of this
latter was found an imperfect ovule--an ovule on an ovule!
Fig. 148 shows a floret of a species of _Gaillardia_, in which the ovule
was replaced by a leafy shoot which had made its way through a chink in
the ovary. In this specimen, however, there was no evidence to show
whether the shoot in question was a perverted development of the
nucleus, or whether it was wholly independent of the ovule.
[Illustration: FIG. 148.--Floret of _Gaillardia_, showing leafy shoot
occupying the place of the ovule.]
From this occasional elongation of the nucleus, as well as from the
foliar nature of the ovular coats, Prof. Alex. Braun arrives at the
conclusion that the ovule is to be looked on as a bud, the ovular
coatings, so often variable in number, representing the scales of the
bud, the nucleus corresponding to the end of the axis or growing point.
Griffith had previously expressed the same opinion from his observations
on malformed ovules of _Sinapis_ and _Lonicera_, while Caspary's
conclusions from the foliaceous ovules of _Trifolum repens_ are somewhat
similar. The latter observer considers that the funiculus, with the
integuments, is the equivalent of a leaflet, the petiolule or midrib of
which answers to the funiculus, and its hollow expansion to the
integument. The nucleus itself is considered to be a new formation
analogous to a shoot.
M. van Tieghem's conclusion[278] from the examination, of flowers of
_Tropaeolum majus_, in which the ovules were replaced by perfect peltate
leaves, is that the ovules are foliar productions springing, not
directly from a prolonged floral axis, as in _Primulaceae_, but from
branches of the axis arising from the axils of the carpellary leaves.
Phyllody of the ovules has been met with most often in the following
species:
*Aquilegia vulgaris!
Skinneri.
Delphinium crassicaule.
elatum.
dictyocarpum.
Ajacis.
Nigella damascena.
Adonis autumnalis.
Cheiranthus Cheiri!
Nasturtium, sp.
Sisymbrium officinale!
Brassica napus!
* olcracea!
*Alliaria officinalis!
Sinapis arvensis!
Turritis, sp.
Thlaspi arvense.
Erucastrum Pollichii.
Stellaria media.
*Reseda lutea.
Drosera intermedia.
Agrostemma Githago.
Stellaria media.
Triumfetta, sp.!
Tropaeolum majus!
Dictamnus albus.
Fraxinella!
Caram carui
Pastinaca sativa.
Torilis anthriscus.
Thysselinum palustre.
Epilobium palustre.
Rosa, sp.
Fragaria alpina.
*Trifolium repens!
Medicago maculata.
Desmodium canadense.
Melilotus macrorhiza.
Lonicera, sp.
Gaillardia!
Crepis, sp.
Phyteuma odorata.
Symphytum Zeyheri.
* officinale.
Stachys sylvatica.
Anagallia arvensis.
phoenicea.
Lysimachia ephemerum.
*Primula sinensis!
Auricula.
praenitens.
Gilia glomeruliflora.
Rumex arifolius.
scutatus.
Salix capraea.
The following list of publications relating to ovular malformations is
copied from A. Braun, 'Ueber Polyembryonie und Keimung von Caelobogyne'
(Appendix),[279] to which are also added some others not alluded to by
that author and not specially referred to in the preceding pages:
Jaeger, 'Missbilld. d. Gewaechse,' p. 78, 79, f. 47. Roeper,
'Enum. Euphorb.,' 1824. p. 45, _Delphinium_.--Schimper,
'Flora,' 1829, pp. 437-8, et 'Mag. fur Pharmacie de Geiger,'
1829-30, pl. iv-vi, text wanting, _Primula_, _Reseda_,
_Cheiranthus_.--Engelmann, 'De Antholysi,' 1832.--Valentin,
'Act. Acad. Nat. Cur.,' 1839, p. 225, _Lysimachia_.--Unger,
'Act. Acad. Nat. Cur.,' xxii, 11, 1850, p. 543, t. 5 B,
_Primula_.--'Flora (B. Z.)', 1842, p. 369, t. ii,
_Trifolium_.--Brongniart, 'Ann. Sc. Nat.,' 1834, ii, p. 308;
also 'Archives Mus. d'Hist. Nat.,' 1844, t. iv, p. 43, pl. iv,
v, _Primula_.--Reissek, 'Linnaea,' xvii, 1843,
_Alliaria_.--Wydler, 'Denkshrift. d. Regensb. Bot. Gesell.,'
1855, iv, s. 77, t. vii, _Alliaria_.--Wigand. 'Grundlegung der
Pflanzen Teratol.,' 1850, p. 39, _Turritis_.--Wigand, 'Bot.
Untersuchungen,' 1853, p. 23, _Rosa_, _Turritis_,
_Crepis_.--Germain de St. Pierre, 'L'lnstitut,' 1853, n. 1051,
p. 351.--Rossmann, "Entwicklung der Eiknospen aus dem
Fruchtblatte," &c., 'Flora,' 1855, pp. 647 and 705.--Dareste,
'Ann. Sc. Nat.,' 1842, p. 220, _Delphinium_.--Fresenius, 'Mus.
Senkenb.,' ii, p. 39, t. iv, f. 9, _Primula_.--Schultz, 'Flora
o. d. Bot. Zeit.,' 1834, xvii, p. 121, _Nasturtium_.--Seringe
and Heyland, 'Bull. Bot.,' 1-7, _Diplotaxis_.--Clos, 'Mem.
Acad. Toulouse,' vi, 1862, _Delphinium_.--Morren, C., 'Bull.
Acad. Belg.,' xix, part ii, p. 519, _Primula_.--Caspary,
'Schrift. d. Physik. OEk. Gesell. zu Koenigsberg,' band ii, p.
51, tabs. ii, iii. Fleischer, 'Ueber Missbildungen
Verschiedener Cultur Pflanzen.,' &c., Esslingen, 1862. Cramer,
'Bildungsabweich,' p. 68, &c. &c., _Trifolium._--Moquin-Tandon,
'El. Terat. Veg.,' p. 206, _Cortusa_.--Guillard, 'Bull. Soc.
Bot. Fr.,' 1857, vol. iv, p. 761, _Stellaria_.--Moelkenboer,
'Tijdschrift v. Natuurl. Geschied.,' 1843, p. 355, t. vi, vii,
_Primula_.--Van Tieghem, 'Bull. Soc. Bot. Fr.,' 1865, p, 411,
_Tropaeolum_.
=Phyllody in accessory organs.=--In addition to the ordinary organs of
the plant, what are termed the accessory organs, such as hairs, spines,
&c., sometimes become foliaceous. It is not to be wondered at that
spines, when they represent the framework of a leaf, become sometimes
clothed with cellular tissue, and thus become indeed true leaves. This
happens occasionally in _Berberis;_ a similar thing occurs in the
stipules of some _Leguminosae_; the scales of some begonias; the tendrils
of _Bignonia_, _Cobaea_, &c.
The presence of two small green laminae on the outer side of the two
posterior stamens in _Antirrhinum majus_ has also been met with. The
adventitious organs appeared as if they were developments from the
thalamus--a kind of foliaceous disc, in fact.
[Illustration: FIG. 149.--Leafy petal of _Epilobium_.]
[Illustration: FIG. 150.--Chloranthy, &c. _Epilobium hirsutum_.]
=Chloranthy.=--The term phyllomorphy is applied to the individual parts
of the flower which assume the form and appearance of leaves. By
chloranthy it is to be understood that all, or the great majority of the
organs of the flower assume these conditions.[280] In chloranthy, as
here defined, there is no unusual number of buds, as there is in
prolification, but the appearance of the flower-bud is so changed as to
make it resemble more closely a leaf-bud than a flower-bud. There is not
necessarily any increase in the number, or any alteration in the
position of the buds, but the form and appearance of the latter differ
from what is usual. Chloranthy, then, is a more complete form of
frondescence. Owing to the vagueness with which the word has been
applied by various authors, it becomes very difficult to ascertain
whether the recorded instances of chloranthy were really illustrations
of what is here meant by that term, or whether they were cases of mere
virescence (green colour, without other perceptible change), or of
prolification (formation of adventitious buds). It is, therefore, quite
possible that some of the instances to be now mentioned were not
strictly cases of chloranthy.
[Illustration: FIG. 151.--_a._ Open leafy carpel of "green rose," with
two deformed ovules. _b._ Ovule separate. _c._ Primine removed. _d._
Secondine and nucleus, with the bulbous end that projects through the
micropyle.]
Seringe[281] has described a malformation in _Diplotaxis tenuifolia_ in
which all the floral organs were replaced by sixteen distinct leaflets
which had preserved their proper relative position. The _Cruciferae_, of
which family the last-named plant is a member, are particularly liable
to this malformation, as also are the _Rosaceae_, as will be seen from
the following illustrations. Roses indeed often exhibit alterations of
this kind as the commencement of prolification. There is also in
cultivation a rose[282] called the green rose, "Rose bengale a fleurs
vertes," in which all the parts of the flower are represented by leaves.
One of the most remarkable features in this plant is, that the carpels
have often two ovules on their margins. Now, Payer, in his
"Organogenie," has shown that at a certain period of the development of
the ordinary rose flower the ovary contains two collateral ovules, of
which one becomes in process of time suppressed.[283] _Geum coccineum_
has been found by Wigand with its flowers in this condition.[284]
Lindley[285] figures a very interesting illustration in _Potentilla
nepalensis_, in which some of the flowers have their component parts
leafy, in others the receptacle lengthens, till in extreme cases the
whole of the floral apparatus is represented by a branch bearing a
rosette of leaves.
A particular variety of the Alpine strawberry is also described as
occasionally subject to this transformation. In these flowers the calyx
remains normal, while all the other parts of the flower, even to the
coating of the ovule, assume a leaf-like condition.[286]
Among _Leguminosae_ a partial leafy condition (frondescence), or a more
complete degree of the same change, (chloranthy) is not infrequent,
particularly in _Trifolium repens_. In this species the changes are so
common, so various and important, that they may be alluded to in some
little detail. M. Germain de Saint Pierre,[287] in commenting on the
frequency with which the flowers of this plant are more or less
frondescent, remarks that although all the flowers on one plant may be
affected, they are all changed in the same manner, but on different
specimens different degrees of transformation are found. In all the
corolla and stamens are comparatively little removed from the ordinary
form, the calyx and pistil, however, have a particular tendency to
assume a foliar condition. The author just cited arranges the
malformations of this plant under three heads, as follows:
1. Calyx-teeth larger than usual, sometimes dentate at the
margin; petals more or less regular and disposed to run away
from the papilionaceous form; filaments free; anthers normal;
carpel transformed into a true leaf with a long stalk provided
at the base, with two stipules, terminal leaflet, solitary,
green, with no trace of ovules. Sometimes a second carpellary
leaf, similar to the first, is formed; in other cases the
central axis of the flower is occasionally prolonged into a
head of young flowers--median prolification. In some few
instances the calyx is not at all altered, but the carpellary
leaf is trifoliolate, or even quinquefoliolate, the corolla
being then absent. The heads of flowers in this first form have
the aspect of little tufts of leaves.
2. Each of the teeth of the calyx is represented by a long
stalk, terminated by a single articulated leaflet, the
bi-labiate form of the calyx is still recognisable; the two
upper petals are united, the three lower separate; the tube of
the calyx is not deformed and seems to be formed of the
petioles of the sepals united by their stipules. In this second
class of cases the corolla is papilionaceous, the filaments
free, the carpellary leaf on a long stalk provided with
stipules, its blade more or less like the usual carpel, with
its margins disunited or more commonly united with the ovules
in the interior, sometimes represented by a foliaceous, dentate
primine only. In one case the carpel was closed above, gaping
below, where it gave origin to several leaflets, the lower ones
oval, dentate, like ordinary leaflets, the upper ones merely
lanceolate, leafy lobes, representing the primine reduced to a
foliaceous condition. Inflorescence--a head with leafy flowers
on long stalks, which are longer at the circumference than in
the centre.
3. Calyx-teeth lance-shaped, acuminate; corolla more or less
regular, arrested in its development and scarcely exceeding the
tube of the calyx within which it is crumpled up; stamens but
little changed; carpellary leaf on a short stalk, not exceeding
the calyx tube, but the ovarian portion very long, and provided
with abortive ovules.
These three groups will be found to include most of the forms
under which frondescence of the clover blossoms occurs, but
there are, of course, intermediate forms not readily to be
grouped under either of the above heads. Such are the cases
brought under the notice of the British Association at
Birmingham in 1849 by Mr. R. Austen, in some of which the
petals and stamens even were represented by leaves.
Although, on the whole, chloranthy is most frequent in the families
already alluded to, yet it is by no means confined to them, as the
examples now to be given amply show. Specimens of _Nymphaea Lotus_ have
been seen in which all the parts of the flower, even to the stigmas,
were leafy, while the ovules were entirely wanting.
Planchon[288] figures and describes a flower of _Drosera intermedia_
that had passed into a chloranthic condition, excepting the calyx, which
was unchanged; the petals, like the valves of the ovary, were provided
with stipules, and were circinate in vernation.
M. A. Viaud-Grand-Marais[289] records an interesting example of
chloranthy, in which the sepals, petals, pistils, and ovules of
_Anagallis arvensis_ were all foliaceous. Similar changes have not
unfrequently been met with in _Dictamnus Fraxinella_.
M. Germain de Saint Pierre has also recorded the following deviations in
the flowers of _Rumex arifolius_ and _R. scutatus_; in these specimens
the calyx was normal, the petals large, foliaceous, shaped like the
stem-leaves, the stamens were absent, the three carpels fused into a
triangular leafy pod, as long again as the perianth, the stigmas normal
or wanting, the ovule represented by a thick funicle, terminated by a
foliaceous appendage analogous to the primine.[290]
In grasses it frequently happens that the flowers are replaced by
leaf-buds; this condition is alluded to elsewhere under the head of
viviparous grasses, but in this place may be mentioned a less degree of
change, and which seems to have been a genuine case of chloranthy in
_Glyceria fluitans_, the spikelet of which, as observed by Wigand,[291]
consisted below of the ordinary unchanged glumes, but the remaining
paleae as well as the lodicles and stamens were represented by ligulate
leaves. The plant, it is stated, was affected by a parasitic fungus. On
the other hand, General Munro, in his valuable monograph of the
_Bambusaceae_,[292] refers to an illustration in which "the lowest glumes
generally, and the lowest paleae occasionally, had the appearance of
miniature leaves, with vaginae, ligules and cilia, enveloping, however,
perfect fertile spiculae; as progress is made towards the top of the
spike, the ligule first, then the cilia, and finally, the leaf-like
extension disappears, and the uppermost glumes assume the ordinary shape
and form of those organs."
=General remarks on chloranthy and frondescence.=--Moquin remarks with
justice that the position of the flowers on the axis is of importance
with reference to the existence of chloranthy. Terminal flowers are more
subject to it than lateral ones, and if the latter, by accident, become
terminal, they seem peculiarly liable to assume a foliaceous condition.
Kirschleger says, that in _Rubus_ there are two sorts of chloranthy,
according as the anomaly affects the ordinary flowering branches, or the
leafy shoots of the year, the summits of which, instead of developing in
the customary manner, terminate each in one vast and long inflorescence,
very loose and indeterminate, and with axillary flowers.[293]
On the whole, taking in consideration cases of partial frondescence, as
well as those in which most of the parts of the flower are affected,
phyllody would seem to be most common in the petals and carpels, least
so in the case of the stamens and sepals. It is more common among
polysepalous and polypetalous plants than in those in which the sepals
or petals are united together.
The causes assigned for these phenomena are chiefly those of a nature to
debilitate or injure the plant; thus it has been frequently observed to
follow the puncture of an insect. M. Guillard[294] gives an instance in
_Stellaria media_ where the condition appeared to be due to the attacks
of an insect _Thrips fasciata_. Still more commonly it arises from the
attacks of parasitic fungi, _e.g._ _Uredo candida_, in Crucifers, &c.
In other cases it has been observed when the plants have been growing in
very damp places, or in very wet seasons, or in the shade, or where the
plant has been much trampled on. This happens frequently with _Trifolium
repens_. The frequency with which the change is encountered in this
particular species is very remarkable; it is difficult to see why one
species should be so much more subject to the kind of change than
another of nearly identical conformation.
It might at first be supposed that the same causes that bring about the
complete substitution of leaf-buds for flower-buds (see Heterotaxy)
would operate also in the partial substitution of leaves for other parts
of the flower, but it will be seen that the inducing cause, whether
similar or not in the two cases respectively, acts at different times;
in the one case, it is not brought into play until the rudiments of the
flower are already formed, whereas in the other the influence is exerted
prior to the formation of the flower. So that while the formation of
leaf-buds in place of flower-buds may be and generally is due to an
excess of nutrition, inducing over activity of the vegetative organs,
the production of phyllomorphic or chloranthic flowers may be owing
rather to a perversion of development arising from injury or from some
debilitating agency. The discrepancies in the assigned causes for the
conditions above mentioned may, therefore, in great measure, be
attributed to the different periods at which the causes in question
operate.
The following list may serve as a guide to the plants most frequently
the subjects of chloranthy, but reference should also be made to
preceding and subsequent sections, and to that relating to prolification
of the inflorescence.
Aquilegia vulgaris.
Chelidonium majus.
Corydalis aurea.
Nymphaea Lotus!
*Brassica oleracea!
Bunias.
Hesperis matronalis.
*Sinapis arvensis!
Sisymbrium officinale.
Erucastrum canariense.
Diplotaxis tenuifolia.
Lychnis dioica!
Cerastium glomeratum!
triviale.
Stellaria media.
Poterium polygamum.
Torilis anthriscus.
Seseli, sp.
Selinum caruifolium.
Epilobium hirsutum!
Begonia fuchsioides.
Gomphia, sp.
Scabiosa Columbaria.
Dipsacus fullonum.
Matricaria Parthenium.
Calendula officinalis.
Campanula pyramidalis.
Reseda odorata!
Vitis vinifera.
Dictamnus Fraxinella!
Triumfetta, sp.!
*Tropaeolum majus!
Rhamnus Frangula.
*Trifolium repens!
Lupinus, sp.
Rosa diversifolia!
Potentilla nepalensis.
argentea.
Fragaria vesca!
Geum rivale.
Rubus fruticosus.
caesius.
Saxifraga foliosa.
Verbascum phlomoides.
Scrophularia nodosa.
aquatica!
*Primula sinensis!
Lysimachia Ephemerum.
Anagallis arvensis.
Webbiana.
Nicotiana rustica.
Anchusa ochroleuca.
Myosotis caespitosa.
Stachys sylvatica.
Gilia capitata.
Euphorbia segetalis.
Rumex arifolius.
scutatus.
Juncus lampocarpus.
uliginosus.
In addition to the publications before cited the following may be named
as containing valuable information on the subject of this chapter.
Jaeger, 'Missbild. Gewaechs.,' 1814, p. 83, _Trifolium repens_.
For other accounts of similar malformations in the same plant,
see Schmitz, 'Linnaea,' xv, p. 268. Unger, 'Flora' (B. Z.) xxv,
p. 369. Caspary, 'Schrift. der. Physik. oekon. Gesellsch. zu
Koenigsberg,' 2, 1861, p. 51, tabs. ii, iii. Fleischer,
'Missbilld. verschied. Cult. Pflanz.,' 1862, p. 55, &c., t. v,
vii, &c. For _Primula_ see Brongniart, 'Ann. Sc. Nat.,' ser. 2,
t. i, p. 308. A. P. and Alph. De Candolle in 'Neue
Denkschrift.' Morren, C., 'Bull. Acad. Roy. Belg.,' xix, part
2, p. 539. Molkenboer, 'Tijdschr. voor Natuurl. Geschied.,'
1843, p. 355, tabs. vi, vii. Marchand, 'Adansonia,' iv, p. 167
and p. 159. _Anagallis_, p. 171, _Lonicera_, p. 83, _Juncus_.
For other plants see Fresenius, 'Mus. Senk.,' 2, p. 35, &c.
Norman, 'Ann. Sc. Nat.,' ser. 4, 1858, vol. ix, p. 220. Christ,
'Flora' (B. Z.) 1867, p. 376, tabs. v, vi, _Stachys_. Cramer,
'Bildungsabweich.,' p. 26, &c. Baillon, 'Adansonia,' ii, p.
300. Moquin-Tandon, 'El. Ter. Veg.,' p. 230. Schauer's
translation, p. 220. Hallier, 'Phytopathologie,' p. 160.
FOOTNOTES:
[245] Engelmann makes use of the word frondescence in the same cases.
'De Anthol.,' p. 32, Sec. 38, while Morren adopts the term Phyllomorphy,
'Lobelia,' p. 95.
[246] See Schlechtendal, 'Bot. Zeit.,' vol. xv, 1857, p. 873; also
Marchand, 'Adansonia,' iv, p. 156.
[247] For instances of similar changes in _Composites_, see De Candolle,
'Prod.,' t. vi, p. 571, _Centaurea Jacea phyllocephala_. Clos, 'Ann. Sc.
Nat.,' ser. iii, tom. xvi, 1851, p. 41. 'Science Gossip,' 1865, p. 104,
&c.
[248] Kickx, 'Bull. Acad. Belg.,' t. xviii, part 2, p. 288.
[249] Weber, 'Verhandl. Nat. Hist. Vereins. f. Preuss.,' &c., 1860, p.
381.
[250] Weber, loc. cit.
[251] Sauter, 'Flora v. Bot. Zeit.,' 1831, p. 11.
[252] 'Descr. et Icon. Plant.' tab. 20.
[253] For references see p. 115; see also to Eichler, 'Excurs.
Morpholog. de format. flor. Gymnosperm.,' in "Mart. Flor. Brasil,"
abstracted in English in 'Natural History Review,' April, 1864.
[254] "Calyx tunc plane non differt a foliis proxime ipsi
praecedentibus." Wolff, 'Theor. Gener.,' Sec. 114. Linn., 'Proleps.,'
Sec. 6. Goethe, 'Versuch.,' Secs. 31-38.
[255] 'Bull. Soc. Bot. France,' vol. viii, 1861, p. 697.
[256] 'Organ. Veget.,' t. i, p. 492, pl. xxxii, f. 6.
[257] This distinction between laminar and vaginal venation is well seen
in cases like _Mussaenda_, _Calycophyllum_, or _Dipterocarpus_, where
the enlarged calycine segment has a strictly vaginal arrangement of its
veins, very different from that which occurs in the true leaf-blades.
These are cases, therefore, where the sheath of the leaf is unusually
enlarged, and are not to be referred, as is often done, to metamorphosis
of one or more sepals to perfect leaves. Prolified roses, cherries, &c.,
furnish frequently parallel cases. With reference to _Mussaenda_, C.
Morren held the view that the petal-like sepal was really a bract
adherent to the calyx, and incorporating with itself one of the calycine
lobes--"soudee au calice et ayant devoree, en englobant dans sa propre
masse, un lobe calicinal." The Belgian _savant_ considers this somewhat
improbable explanation as supported by a case wherein there were five
calyx lobes of uniform size, and a detached feather-veined leaf
proceeding from the side of the ovary lower down ('Bull. Acad. Belg.,'
xvii, p. 17, _Fuchsia_, p. 169).
[258] In this order _Agrostemma Githago_ offers an illustration of a
normally leafy calyx.
[259] 'Bull. Bot.,' i, p. 6.
[260] Wolff's original opinion was that the stamens were equivalent to
so many buds placed in the axil of the petals or sepals (see 'Theoria
Generationis,' 1759, Sec. 114)--an opinion which more recently has received
the support of Agardh and Endlicher. Wolff himself, however, seems to
have abandoned his original notion, for in his memoir, "De formatione
intestinorum praecipue tum et de amnio spurio aliisque partibus embryonis
gallinacei, nondum visis," &c., in 'Comm. Acad. Petrop.,' xii, p. 403,
anno 1766, he considers the stamens as essentially leaves. See also
Linn. 'Prolepsis,' Sec. viii; Goethe, 'Metam.,' Sec. 46.
[261] Mueller (Argov.), in 'Mem. Soc. Phys. et d'Hist. Nat. Genev.,' t.
xvii.
[262] "If we keep in view the observations which have now been made, we
shall not fail to recognise the leaf in all seed-vessels,
notwithstanding their manifold forms, their variable structure, and
different combinations."--(Goethe, 'Metam.,' Sec. 78.) Wolff, 'N. Comm.
Acad. Petrop.,' 1766, xii, p. 403, expresses precisely the same opinion
as to the nature of the seed-vessel.
[263] 'El. Terat. Veg.,' p. 205.
[264] 'Ann. Sc. Nat.,' 4th series, vol. ix, p. 209.
[265] 'Adansonia,' iv, p. 70. A similar deviation has been observed by
M. van Tieghem in the ovary of _Tropaeolum majus_, 'Bull. Soc. Bot. Fr.,'
1865, p. 411.
[266] Planchon et Mares, 'Ann. Sc. Nat.,' ser. 5, vol. vi, 1866, p. 228,
tab. xii.
[267] 'Act. Acad. Nat. Cur.,' 22, 11. 1850, p. 543, t. v, vi.
[268] 'Neue Denkschrift der allg. Schweiz. Gesellsch.,' band v. p. 9,
tab. 3, 4.
[269] 'Ann. Sc. Nat.,' 2 ser., vol. i, p. 308, pl. ix, c.
[270] 'Adansonia,' vol. iv, pp. 159, 171.
[271] 'Bildungsabweichungen,' &c., tab. iv, figs. 1, 2, 21, 28, 29, &c.
[272] 'Bull. Soc. Bot. France,' viii, p. 395.
[273] 'Notulae,' p. 125, atlas, pl. xxxv; and 'Journals of Travels,'
1847, p. 475, _Lonicera_.
[274] 'Ann. Science Nat.,' 3rd ser., vol. ix, p. 86, tabs. 5, 6.
[275] 'Comptes Rendus,' vol. xviii, March 25th, 1864, and 'Ann. Sc.
Nat.,' 3 ser., vol. ii, p. 32.
[276] 'Mem. Acad. Sc. Toulous.,' ser. 5, vol. iii.
[277] 'Bildungsabweich. Pflanz. Famil.,' p. 89, tab. xi.
[278] 'Bull. Soc. Bot. Fr.,' 1865, p. 411.
[279] Translated in 'Ann. Sc. Nat.,' 4th series, t. xiv, p. 24.
[280] The calyx is not unfrequently excepted.
[281] 'Bull. Bot.,' t. i, p. 6.
[282] Lindley, 'Theor. Horticult.,' ed. 2, p. 84, f. 17.
[283] Gris, 'Bull. Soc. Bot. Fr.,' 1858, vol. v, p. 261, and 'Ann. Sc.
Nat.,' ser. 4, vol. ix, p. 80. Planchon, 'Flore des Serres,' vol. i,
1856, p. 129.
[284] 'Flora,' 1856, p. 711.
[285] 'Theory of Horticult.,' ed. 2, p. 90, f. 25.
[286] As considerable interest attaches to the "Plymouth strawberry,"
and very little is known of it in this country, or on the continent, the
author gladly avails himself of this opportunity of inserting an account
of it, for which he is indebted to the kindness of Dr. Robert Hogg.--The
Plymouth Strawberry (_Fragaria vesca fructu hispido_) is a sort of
botanical Dodo upon which many have written, and which few have seen.
Many years have elapsed since it was first discovered; and although a
century and a half have passed since there was any evidence of its
existence, it serves still as an illustration for students in morphology
of one of those strange abnormal structures with which the vegetable
kingdom abounds.
It is to old John Tradescant we are indebted for the earliest record of
this plant. Johnson, in his edition of 'Gerard,' says; "Mr. John
Tradescant hath told me that he was the first that tooke notice of this
strawberry, and that in a woman's garden at Plimouth, whose daughter had
gathered and set the roots in her garden, in stead of the common
strawberry; but she, finding the fruit not to answer her expectation,
intended to throw it away; which labour he spared her in taking it and
bestowing it among the louers of such varieties, in whose garden it is
yet preserved." Doubtless one of those "lovers" was his friend John
Parkinson, who, in the year 1629, thus wrote concerning it: "One
strawberry more I promised to shew you, which, although it be a wilde
kinde, and of no vse for meate, yet I would not let this discourse passe
without giuing you the knowledge of it. It is in leafe much like vnto
the ordinary, but differeth in that the flower, if it haue any, is
greene, or rather it beareth a small head of greene leaues, many set
thicke together like vnto a double ruffe, in the midst whereof standeth
the fruit, which, when it is ripe, sheweth to be soft and somewhat
reddish, like vnto a strawberry, but with many small harmlesse prickles
on them which may be eaten and chewed in the mouth without any maner of
offence and is somewhat pleasant as a strawberry; it is no great bearer,
but those it doth beare, are set at the toppes of the stalks close
together, pleasant to behold, and fit for a gentlewoman to weare on her
arme, &c., as a rairitie in stead of a flower."
Merret, in his 'Pinax.' published in 1667, says he found it growing in
the woods of Hyde Park and Hampstead, and Zanoni was the first to figure
it (with the exception of Parkinson's rude woodcut) in his 'Istoria
Botanica,' published in 1675. It is mentioned by Morison and also by
Ray, the latter of whom inserts it in his Synopsis, but without any
habitat; though in his 'Historia Plantarum' he says: "Cantabrigiae in
horto per aliquot annos colui." From this time henceforth the Plymouth
strawberry has become a botanical Dodo, nothing more having been seen or
heard of it except the mere record of the name. In 1766, M. Duchesne
informed the world of the generosity of "M. Monti, Docteur de
Philosophie et de Medecine a Boulogne en Italie," who divided with him a
dried specimen taken from his own herbarium, "Ce present pretieux m'ote
toute incertitude sur la nature de ce Fraisier et sur ses caracteres
monstrueux. Il paroit ne pas avoir aujourd'hui plus d'existence."
[287] 'Bull. Soc. Bot. France,' 1856, vol. iii, p. 477.
[288] 'Ann. Sc. Nat.,' 3 ser., vol. ix, p. 86, tabs. v, vi.
[289] 'Bull. Soc. Bot. France,' vol. viii, 1861, p. 695.
[290] Ibid., vol. iii, 1856, p. 475.
[291] 'Flora,' 1856, p. 712.
[292] 'Trans. Linn. Soc.,' vol. xxvi, p. 37.
[293] 'Bull. Soc. Bot. France,' 1862, vol. ix, p. 36, tab. i, and also
p. 291.
[294] Ibid., 1857, vol. iv, p. 761.
CHAPTER II.
METAMORPHY OF THE FLORAL ORGANS.
One of the main arguments adduced by Goethe and others in support of the
now generally received doctrine of the essential morphological identity
of the various whorls of the flower is derived from the frequent
appearance of one organ in the guise of another. The several parts of
the flower become, as it is said, metamorphosed; sometimes the change
is complete, while at other times there may be every conceivable
intermediate condition between one form and another. The sense in which
the terms metamorphosis, substitution, transformation, and the like, are
herein used has already been explained. For the convenience of
arrangement, metamorphosis of the parts of the flower may be divided
into several subdivisions, according to the particular organ affected,
and according to the special kind or degree of change manifested, the
main subdivisions being here classed as Sepalody, Petalody, Staminody,
and Pistillody.
=Sepalody of the petals.=--This change, spoken of by most authors as
retrograde metamorphosis of the petals into sepals, or as a substitution
of sepals for petals, is obviously a condition that is in most cases
hardly distinguishable from virescence of the corolla, or from
multiplication of the sepals. Nor is this of much consequence unless
there are some special structural features which render the
discrimination a matter of importance, in which case the difficulty is
generally easily surmounted. The flower of the Saint-Valery Apple may
perhaps be cited under this head. In the flower in question there are
neither stamens nor petals, unless the second or inner of sepals be
considered as sepaloid petals (fig. 152).
[Illustration: FIG. 152.--Flower of St. Valery apple, with sepaloid
petals.]
M. Alph. de Candolle[295] describes an instance in _Primula Auricula_ in
which the corolla had assumed the appearance of the calyx, but neither
calyx nor corolla in this case possessed perfect stomata.
This malformation is much less common than the converse one of
calycanthemy. Many of the recorded instances of so-called metamorphosis
of the parts of the flower to sepals have occurred in monocotyledonous
plants, or others in which the calyx and corolla are of the same colour,
and constitute what is frequently termed the perianth; and as this is
usually brightly coloured (not green) it is more convenient to group the
metamorphoses in question under the general term Petalody, which thus
includes all those cases in which the organs of the flower appear in the
form of coloured petal-like organs, whether they be true petals or
segments of a coloured perianth. As the morphological difference between
the organs is one of position merely, there is little objection to be
raised to this course, the less so as the term petalody merely conveys
an idea of resemblance and not of absolute identity.
Petaloid coloration of the ordinary leaves, or of the bracts, is
mentioned under the chapter relating to colour.
=Petalody of the calyx--Calycanthemy.=--As with the bracts, so the calyx
in certain instances is naturally coloured, as in _Delphinium_,
_Tropaeolum_, and others. In _Mussaenda_, _Calycophyllum_, _Usteria_, &c.,
one or more of the calyx lobes become enlarged normally. Considered
teratologically, petaloid coloration of the sepals is either general or
partial; in the latter case the nerves retain their green colour
longest. There is in cultivation a variety of the primrose called
_Primula calycanthema_, in which the upper part of the calyx becomes
coloured, so that the flower seems to have two corollas placed one
within the other; a similar thing happens in _Mimulus_, in which plant,
as the calyx is permanent while the corolla is deciduous, the coloured
calyx is a great advantage in a horticultural point of view. Morren[296]
says that in order to produce the fine colour of the calyx of _Primula
officinalis_ (var. _smaragdina_) the Belgian gardeners cut away the
corolla in a very early stage, and that in consequence the colouring
matter proper to the corolla is developed in the tube of the calyx, the
edges of the limb remaining green, the middle of the limb being purple
(_Primula tricolor_).
[Illustration: FIG. 153.--Flower of _Mimulus_, with petaloid calyx.]
Under this head may be mentioned the occurrence of tubular sepals in
place of the ordinary flat ones in _Helleborus olympicus_; only two of
the sepals were thus affected in a specimen recently observed--a third
exhibited an intermediate condition.
The normal coloration of the calyx occurs most frequently in
polysepalous calyces; teratological coloration, on the other hand,
occurs especially in gamosepalous flowers. This assertion is borne out
by the frequency of the change in the plants already mentioned, and also
in the following:--_Campanula persicifolia_, _Anagallis arvensis_,
_Gloxinia_, _Syringa persica_,[297] _Calceolaria_, _&c. &c_. In the
last-named plant one or more of the lobes of the calyx may frequently be
seen replaced by a slipper-like petal.
Among polysepalous plants petaloid sepals have been observed in
_Ranunculus auricomus_, _Rubus caesius_, _&c._ Fleischer also describes a
case of this kind in _Carum carui_.[298]
It will be seen from the above that in the majority of cases there is no
real metamorphosis or substitution of petal for calyx, but simply an
alteration in colour; nevertheless, a change in form may accompany a
change of colour: this happens especially if there has been any
displacement of organs. Thus, if, in an orchidaceous plant, a sepal be
displaced from any cause, or a petal be twisted out of its natural
position to occupy the place of an absent sepal, that petal will be
sepal-like in form, and _vice versa_.
=Petalody of the stamens.=--A petaloid condition of the stamens is one
of the commonest of all malformations. A large number of so-called
double flowers (flores pleni)[299] owe their peculiar appearance to this
circumstance.
It is necessary to distinguish carefully this petaloid development of
the stamens from the corresponding condition of the pistils, and from
that kind of doubling which is a result of multiplication of the
corolla, as in _Datura_, _Campanula_, _Primula_, &c. (flores duplices,
triplices, &c.), or from that produced by true median prolification
(flores geminati, &c.).
In cases of true petaloid development of the stamens there are usually
numerous intermediate forms between that of the true petals and that of
the perfect stamens; indeed, in _Nymphaea_, _Canna_, and in some other
plants, such a transition occurs normally. Petalody of the stamens may
occur either without material change in the flower or it may exist in
combination or in conjunction with an increased development of parts
(Multiplication), or with a similar change in the carpels, and it is
either partial or complete.
Among the flowers in which petaloid development of the stamens happens
most frequently may be mentioned those in which the calyx is normally
coloured, as in _Nigella damascena_, _Aguilegia_, and _Delphinium_.
M. Alph. de Candolle, in the 'Neue Denkschriften,' 1841, described and
figured a singular form of _Viola odorata_, known under the name of
"Bruneau," in Switzerland, in which the stamens are absent, and their
place supplied by a second row of petals, within which is a third series
of petals, representing, says M. de Candolle, the inner row of stamens
that theory suggests should exist in the natural condition. Moreover,
the carpels in this variety are five in number instead of three. In
_Erica Tetralix_ the corolla may not unfrequently be found divided to
the base into its constituent petals, and the place of the stamens
occupied by a series of petal-like structures entirely destitute of
anther.
In monocotyledonous flowers, especially those with a coloured perianth,
the substitution of segments of the perianth for stamens occurs not
unfrequently. M. Seringe has observed this in the stamens of _Lilium
Martagon_, and there is in cultivation a variety of the white lily,
_Lilium candidum_, sometimes called the double white lily, in which the
segments of the perianth, in place of being arranged in two rows, are
greatly increased in number, and disposed in a spiral manner. In these
flowers, not only are the stamens and pistils thus modified, but also
the upper leaves of the stem. In so-called double tulips there is
likewise a replacement of stamens by coloured segments of the perianth,
but this happens generally in connection with an increase in the number
of organs. Moquin-Tandon remarks having seen in a garden in the environs
of Montpelier a tulip, the stamens of which showed all possible stages
of transition between the form proper to them and that of the perianth.
The pistil in this case was transformed into several small leaves.
Similar appearances have been observed in Iris, Hyacinths, Narcissus,
Colchicum, and Crocus. M. Fournier[300] describes a flower of _Narcissus
Tazetta_ from within the normal perianth of which sprang a second one,
equally provided with a cup and occupying the space usually filled by
the stamens. Flowers of _Narcissus poeticus_ may also be met with in
which the stamens are replaced by six distinct segments exactly
resembling those of the perianth in miniature.[301]
[Illustration: FIG. 154.--Double columbine, _Aquilegia_--petalody of the
filament.]
From an examination of these flowers it becomes evident that
petalification is brought about in different flowers in different ways;
sometimes it is the filament which becomes petaloid, sometimes the
anther-lobes, while at other times it is the connective which assumes
the appearance of petals.[302] For instance, in _Solanum tuberosum_,
_S. Dulcamara_, in _Anagallis_, in _Fuchsia_, and some other plants, the
anther-lobes themselves become petaloid, while the filament remains
unchanged.
In gardens two distinct varieties of Columbine are cultivated, the one
in which the filaments are dilated into the form of flat petals almost
entirely or quite destitute of anthers, while in the other the filament
is present in its usual form, but the anther is developed in the shape
of a tubular hood or spur.
De Candolle[303] observes that in the _Ranunculaceae_ the species of
_Clematis_ become double by the expansion of the filament, those of
_Ranunculus_ by the dilatation of the anther, and those of _Helleborus_
by the petal-like development of both filament and anther. In some cases
even on the same plant all three modifications may be seen, as in
Camellias, some of which may be found with petaloid filaments with
anthers on the top, others with the filaments unchanged, but supporting
petaloid anthers, while in others it is the connective alone which is
petal-like. Where the flower naturally contains a large number of
stamens, as in Mallows, Roses, Magnolias, &c., petaloid expansion of the
filament is most common, though it is by no means confined to such
flowers, the change occurring in _Allamanda cathartica_, _Jasminum
grandiflorum_, and many other flowers with few stamens. A similar change
in the anther and connective takes place more frequently in flowers
where the number of stamens is smaller, but there are of course numerous
exceptions to this rule.
In those cases where there is more than one row of stamens, the
outermost are most liable to this change: thus in _Saxifraga decipiens_,
as shown by Ch. Morren,[304] the outer series of stamens--those opposite
to the sepals--become first affected, and, at a more advanced stage, the
inner row also; and this is the case in most flowers that have their
stamens in two rows. Occasionally it happens that an outer series of
stamens is abortive, or wholly suppressed, while the inner row becomes
petalodic; this was the case in some flowers of _Lilium auratum_ lately
exhibited by Messrs. Veitch.
Those flowers in which only a portion of the stamens undergo this change
are called semi-double, while in other cases that will be hereafter
mentioned, not only are the stamens thus rendered petaloid, but their
number is also augmented, as in most double roses, pinks, anemones,
poppies, &c.